C++程序设计（第3版）谭浩强 第6章 习题
1.输入3个整数，按由小到大的顺序输出。
【解】
#include
using namespace std;
int main()
{
void swap(int *p1, int *p2);
int n1, n2, n3;
int *p1, *p2, *p3;
cout << "input three integers n1,n2,n3:";
cin >> n1 >> n2 >> n3;
p1 = &n1;
p2 = &n2;
p3 = &n3;
if (n1 > n2) swap(p1, p2);
if (n1 > n3) swap(p1, p3);
if (n2 > n3) swap(p2, p3);
cout << "Now,the order is:" << n1 << " " << n2 << " " << n3 << endl;
return 0;
}
void swap(int *p1, int *p2)
{
int p;
p = *p1; *p1 = *p2; *p2 = p;
} 运行结果：
//input three integers n1, n2, n3:54 –12 2↙
//Now, the order is : –12 2 54
2.输入3个字符串，按由小到大的顺序输出。
【解】
//（1）用字符数组方法
#include
#include
using namespace std;
int main()
{
void swap(char *, char *);
char str1[20], str2[20], str3[20];
cout << "input three line:" << endl;
gets(str1);
gets(str2);
gets(str3);
if (strcmp(str1, str2) > 0) swap(str1, str2);
if (strcmp(str1, str3) > 0) swap(str1, str3);
if (strcmp(str2, str3) > 0) swap(str2, str3);
cout << endl << "Now,the order is:" << endl;
cout << str1 << endl << str2 << endl << str3 << endl;
return 0;
}
void swap(char *p1, char *p2) //交换两个字符串
{
char p[20];
strcpy(p, p1); strcpy(p1, p2); strcpy(p2, p);
}
//（2）用string方法，程序中使用了指针和引用
#include
#include
using namespace std;
int main()
{
void change(string &, string &);
string str1 = " ",
str2 = " ",
str3 = " ";
char *p1 = &str1[0], *p2 = &str2[0], *p3 = &str3[0];
cout << "input three line:" << endl;
gets(p1);
gets(p2);
gets(p3);
if (str1 > str2)change(str1, str2);
if (str1 > str3)change(str1, str3);
if (str2 > str3)change(str2, str3);
cout << endl << "Now,the order is:" << endl;
cout << str1 << endl << str2 << endl << str3 << endl;
return 0;
}
void change(string &st1, string &st2) //交换两个字符串。形参为引用变量
{
string st;
st = st1; st1 = st2; st2 = st;
} 运行结果：
//input three line :
//I study very hard.↙
//C language is very interesting.↙
//He is a professor.↙
//
//Now, the order is :
//C language is very interesting.
//He is a professor.
//I study very hard.
3.输入10个整数，将其中最小的数与第1个数对换，把最大的数与最后一个数对换。写3个函数: ①输入10个数； ②进行处理； ③输出10个数。
【解】
#include
using namespace std;
int main()
{
void input(int *number);
void max_min_value(int *number);
void output(int *number);
int number[10];
input(number); //调用输入10个数的函数
max_min_value(number); //调用交换函数
output(number); //调用输出函数
return 0;
}
void input(int *number) //输入10个数的函数, 形参number为指针变量
{
int i;
cout << "input 10 numbers:";
for (i = 0; i < 10; i++)
cin >> number[i];
}
void max_min_value(int *number) //交换函数
{
int *max, *min, *p, temp;
max = min = number; //使max和min都指向number[0]
for (p = number + 1; p < number + 10; p++)
if (*p > *max) max = p; //将大数地址赋给 max
else if (*p < *min) min = p; //将小数地址赋给 min
temp = number[0]; number[0] = *min; *min = temp; //将最小数与第一个数交换
if (max == number) max = min; //如果第一个数刚好是最大数, 则使max指向该最大数
temp = number[9]; number[9] = *max; *max = temp; //将最大数与最后一个数交换
}
void output(int *number) //输出函数
{
int *p;
cout << "now,they are: ";
for (p = number; p < number + 10; p++)
cout << *p << " ";
cout << endl;
return;
} 运行结果：
//input 10 numbers:84 72 45 67 81 19 96 64 42 83↙
//Now, they are : 19 72 45 67 81 84 83 64 42 96
4.有ｎ个整数，使前面各数顺序向后移m个位置，最后m个数变成最前面m个数，见图6.1。写一函数实现以上功能，在主函数中输入n个整数，并输出调整后的n个数。
【解】
#include
using namespace std;
int main()
{
void move(int *, int, int);
int number[20], n, m, i;
cout << "how many numbers?"; //询问共有多少个数
cin >> n;
cout << "input " << n << " numbers:" << endl; //要求输入n个数
for (i = 0; i < n; i++)
cin >> number[i];
cout << "how many places do you want move?"; //询问后移多少个位置
cin >> m;
move(number, n, m); //调用move 函数
cout << "Now,they are:" << endl;
for (i = 0; i < n; i++)
cout << number[i] << " ";
cout << endl;
return 0;
}
void move(int *array, int n, int m) //使循环后移一次的函数
{
int *p, array_end;
array_end = *(array + n - 1);
for (p = array + n - 1; p > array; p--)
*p = *(p - 1);
*array = array_end;
m--;
if (m > 0) move(array, n, m); //递归调用, 当循环次数m减至为0时, 停止调用
} 运行结果：
//how many numbers ? 9↙
//input 8 numbers :
//12 43 –34 65 67 8 2 7 11↙
//how many places do you want move ? 3↙
//Now, they are :
//2 7 11 12 43 –34 65 67 8
5.有n个人围成一圈，顺序排号。从第1个人开始报数（从1～3报数），凡报到3的人退出圈子，问最后留下的人原来排在第几号。
【解】
#include
using namespace std;
int main()
{
int i, k, m, n, num[50], *p;
cout << "input number of person: n=";
cin >> n;
p = num;
for (i = 0; i < n; i++)
*(p + i) = i + 1; //以1至n为序给每个人编号
i = 0; //i为每次循环时计数变量
k = 0; //k为按1,2,3报数时的计数变量
m = 0; //m为退出人数
while (m < n - 1) //当退出人数比n–1少时（即未退出人数大于1时）执行循环体
{
if (*(p + i) != 0) k++;
if (k == 3) //将退出的人的编号置为0
{
*(p + i) = 0;
k = 0;
m++;
}
i++;
if (i == n) i = 0; //报数到尾后, i恢复为0
}
while (*p == 0) p++;
cout << "The last one is NO." << *p << endl;
return 0;
} 运行结果：
//input number of person : n = 8↙
//The last one is NO.7 （最后留在圈子内的是7号）
6.写一函数，求一个字符串的长度。在main函数中输入字符串，并输出其长度。
【解】
#include
using namespace std;
int main()
{
int length(char *p);
int len;
char str[20];
cout << "input string:";
cin >> str;
len = length(str);
cout << "The length of string is " << len << "." << endl;
return 0;
}
int length(char *p) //求字符串长度的函数
{
int n;
n = 0;
while (*p != '\0')
{
n++;
p++;
}
return(n);
} 运行结果：
//input string : Beijing↙
//The length of string is 7.
7.有一字符串，包含n个字符。写一函数，将此字符串中从第m个字符开始的全部字符复制成为另一个字符串。
【解】
#include
using namespace std;
int main()
{
void copystr(char *, char *, int);
int m;
char str1[20], str2[20];
cout << "input string:";
gets(str1);
cout << "which character do you want begin to copy?";
cin >> m;
if (strlen(str1) < m)
cout << "input error!" << endl;
else
{
copystr(str1, str2, m);
cout << "result:" << str2 << endl;
}
return 0;
}
void copystr(char *p1, char *p2, int m) //字符串部分复制函数
{
int n;
n = 0;
while (n < m - 1)
{
n++;
p1++;
}
while (*p1 != '\0')
{
*p2 = *p1;
p1++;
p2++;
}
*p2 = '\0';
} 运行结果：
//input string : countryside↙
//which character do you want begin to copy ? 8↙
//result : side
8.输入一行文字，找出其中大写字母、小写字母、空格、数字以及其他字符各有多少。
【解】
#include
using namespace std;
int main()
{
int upper = 0, lower = 0, digit = 0, space = 0, other = 0, i = 0;
char *p, s[20];
cout << "input string:";
while ((s[i] = getchar()) != '\n') i++;
p = &s[0];
while (*p != '\n')
{
if (('A' <= *p) && (*p <= 'Z'))
++upper;
else if (('a' <= *p) && (*p <= 'z'))
++lower;
else if (*p == ' ')
++space;
else if ((*p <= '9') && (*p >= '0'))
++digit;
else
++other;
p++;
}
cout << "upper case:" << upper << endl << "lower case:" << lower << endl;
cout << "space:" << space << endl << "digit:" << digit << endl << "other:" << other << endl;
return 0;
} 运行结果：
//input string : Today is 2012 / 1 / 1↙
//upper case:1
//lower case:6
//space : 2
//digit : 6
//other : 2
9.写一函数，将一个3×3的整型矩阵转置。
【解】
#include
using namespace std;
int main()
{
void move(int *);
int a[3][3], *p, i;
cout << "input matrix:" << endl;
for (i = 0; i < 3; i++)
cin >> a[i][0] >> a[i][1] >> a[i][2]; //输入一行的3个元素
p = &a[0][0];
move(p);
cout << "Now,matrix:" << endl;
for (i = 0; i < 3; i++)
cout << a[i][0] << " " << a[i][1] << " " << a[i][2] << endl;
cout << endl;
return 0;
}
void move(int *pointer)
{
int i, j, t;
for (i = 0; i < 3; i++)
for (j = i; j < 3; j++)
{
t = *(pointer + 3 * i + j);
*(pointer + 3 * i + j) = *(pointer + 3 * j + i);
*(pointer + 3 * j + i) = t;
}
} 运行结果：
//input matrix :
//1 2 3↙
//4 5 6↙
//7 8 9↙
//Now, matrix :
//1 4 7
//2 5 8
//3 6 9
10.将一个5×5的矩阵中最大的元素放在中心，4个角分别放4个最小的元素（按从左到右、从上到下顺序依次从小到大存放），写一函数实现。用main函数调用。
【解】
#include
using namespace std;
int main()
{
void change(int *p);
int a[5][5], *p, i, j;
cout << "input matrix:" << endl;
for (i = 0; i < 5; i++) //输入矩阵
for (j = 0; j < 5; j++)
cin >> a[i][j];
p = &a[0][0]; //使p指向0行0列元素
change(p); //调用函数, 实现交换
cout << "Now,matrix:" << endl;
for (i = 0; i < 5; i++) //输出已交换的矩阵
{
for (j = 0; j < 5; j++)
cout << a[i][j] << " ";
cout << endl;
}
return 0;
}
void change(int *p) //交换函数
{
int i, j, temp;
int *pmax, *pmin;
pmax = p;
pmin = p;
for (i = 0; i < 5; i++) //找最大值和最小值的地址, 并赋给pmax,pmin
for (j = i; j < 5; j++)
{
if (*pmax < *(p + 5 * i + j)) pmax = p + 5 * i + j;
if (*pmin > *(p + 5 * i + j)) pmin = p + 5 * i + j;
}
temp = *(p + 12); //将最大值与中心元素互换
*(p + 12) = *pmax;
*pmax = temp;
temp = *p; //将最小值与左上角元素互换
*p = *pmin;
*pmin = temp;
pmin = p + 1;
//将a[0][1]的地址赋给pmin, 从该位置开始找最小的元素
for (i = 0; i < 5; i++) //找第二最小值的地址赋给 pmin
for (j = 0; j < 5; j++)
if (((p + 5 * i + j) != p) && (*pmin > *(p + 5 * i + j))) pmin = p + 5 * i + j;
temp = *pmin; //将第二最小值与右上角元素互换
*pmin = *(p + 4);
*(p + 4) = temp;
pmin = p + 1;
for (i = 0; i < 5; i++) //找第三最小值的地址赋给pmin
for (j = 0; j < 5; j++)
if (((p + 5 * i + j) != (p + 4)) && ((p + 5 * i + j) != p) && (*pmin > *(p + 5 * i + j))) pmin = p + 5 * i + j;
temp = *pmin; //将第三最小值与左下角元素互换
*pmin = *(p + 20);
*(p + 20) = temp;
pmin = p + 1;
for (i = 0; i < 5; i++) //找第四最小值的地址赋给pmin
for (j = 0; j < 5; j++)
if (((p + 5 * i + j) != p) && ((p + 5 * i + j) != (p + 4)) && ((p + 5 * i + j) != (p + 20)) && *pmin > *(p + 5 * i + j))
pmin = p + 5 * i + j;
temp = *pmin; //将第四最小值与右下角元素互换
*pmin = *(p + 24);
*(p + 24) = temp;
} 运行结果：
//input matrix :
//35 34 33 32 31↙
//30 29 28 27 26↙
//25 24 23 22 21↙
//20 19 18 17 16↙
//15 14 13 12 11↙
//Now, matrix：
//11 34 33 32 12
//30 29 28 27 26
//25 24 35 22 21
//20 19 18 17 16
//13 23 15 31 14
11.在主函数中输入10个等长的字符串。用另一函数对它们排序。然后在主函数输出这10个已排好序的字符串。
【解】
#include
using namespace std;
int main()
{
void sort(char s[][6]);
int i;
char str[10][6];
cout << "input 10 strings:" << endl;
for (i = 0; i < 10; i++)
cin >> str[i];
sort(str);
cout << "Now,the sequence is:" << endl;
for (i = 0; i < 10; i++)
cout << str[i] << endl;
return 0;
}
void sort(char s[][6])
{
int i, j;
char *p, temp[10];
p = temp;
for (i = 0; i < 9; i++)
for (j = 0; j < 9 - i; j++)
if (strcmp(s[j], s[j + 1]) > 0)
{
strcpy(p, s[j]);
strcpy(s[j], s[+j + 1]);
strcpy(s[j + 1], p);
}
}
//（2）用指向一维数组的指针作函数参数
#include
using namespace std;
int main()
{
void sort(char(*p)[6]);
int i;
char str[10][6];
char(*p)[6]; // p是指向由6个元素组成的一维数组的指针
cout << "input 10 strings:" << endl;
for (i = 0; i < 10; i++)
cin >> str[i];
p = str; //p指向二维数组str的0行元素
sort(p);
cout << "Now,the sequence is:" << endl;
for (i = 0; i < 10; i++)
cout << str[i] << endl;
return 0;
}
void sort(char(*s)[6]) //形参q是指向由6个元素组成的一维数组的指针
{
int i, j;
char temp[6], *t = temp;
for (i = 0; i < 9; i++)
for (j = 0; j < 9 - i; j++)
if (strcmp(s[j], s[j + 1]) > 0)
{
strcpy(t, s[j]); //以下3行的作用是将s[j]指向的一维数组的内容
strcpy(s[j], s[+j + 1]); //与s[j+1]指向的一维数组的内容互换
strcpy(s[j + 1], t);
}
}
//（3）用string数组
#include
#include
using namespace std;
int main()
{
void sort(string *);
int i;
string str[10], *p = str; //str为string型数组, p为指向string型变量的指针
cout << "input 10 strings:" << endl;
for (i = 0; i < 10; i++)
cin >> str[i];
sort(p);
cout << "Now,the sequence is:" << endl;
for (i = 0; i < 10; i++)
cout << str[i] << endl;
return 0;
}
void sort(string *s) //形参为指向string型变量的指针
{
int i, j;
string temp;
for (i = 0; i < 9; i++)
for (j = 0; j < 9 - i; j++)
if (s[j] > s[j + 1])
{
temp = s[j];
s[j] = s[+j + 1];
s[j + 1] = temp;
}
} 运行结果：
//input 10 strings:
//China↙
//Japan↙
//Korea↙
//Egypt↙
//Nepal↙
//Burma↙
//Ghana↙
//Sudan↙
//Italy↙
//Libya↙
//Now, the sequence is :
//Burma
//China
//Egypt
//Ghana
//Italy
//Japan
//Korea
//Libya
//Nepal
//Sudan
12.用指针数组处理第11题，字符串不等长。
【解】
#include
using namespace std;
int main()
{
void sort(char *[]);
int i;
char *p[10], str[10][20]; //p为指针数组, 有10个元素
for (i = 0; i < 10; i++)
p[i] = str[i]; //将第i个字符串的首地址赋予指针数组p的第i个元素
cout << "input 10 strings:" << endl;
for (i = 0; i < 10; i++)
cin >> p[i];
sort(p);
cout << "Now,the sequence is:" << endl;
for (i = 0; i < 10; i++)
cout << p[i] << endl;
return 0;
}
void sort(char *s[])
{
int i, j;
char *temp;
for (i = 0; i < 9; i++)
for (j = 0; j < 9 - i; j++)
if (strcmp(*(s + j), *(s + j + 1)) > 0)
{
temp = *(s + j);
*(s + j) = *(s + j + 1);
*(s + j + 1) = temp;
}
} 13.写一个用矩形法求定积分的通用函数，分别求 ∫10sinxdx,∫1-1cosxdx,∫20exdx（说明: sin,cos,exp已在系统的数学函数库中，程序开头要用#include）。
【解】
#include
#include
using namespace std;
int main()
{
float integral(float(*p)(float), float a, float b, int n); //对integral函数作声明
float fsin(float); //对fsin函数作声明
float fcos(float); //对fcos函数作声明
float fexp(float); //对fexp函数作声明
float a1, b1, a2, b2, a3, b3, c, (*p)(float);
int n = 20;
cout << "input a1,b1:"; //输入求sin(x)定积分的下限和上限
cin >> a1 >> b1;
cout << "input a2,b2:"; //输入求cos(x)定积分的下限和上限
cin >> a2 >> b2;
cout << "input a3,b3:"; //输入求ex定积分的下限和上限
cin >> a3 >> b3;
p = fsin;
c = integral(p, a1, b1, n); //求出sin(x)的定积分
cout << "The integral of sin(x) is :" << c << endl;
p = fcos;
c = integral(p, a2, b2, n); //求出cos(x)的定积分
cout << "The integral of cos(x) is :" << c << endl;;
p = fexp;
c = integral(p, a3, b3, n); //求出ex的定积分
cout << "The integral of exp(x) is :" << c << endl;
return 0;
}
float integral(float(*p)(float), float a, float b, int n) //用矩形法求定积分的通用函数
{
int i;
float x, h, s;
h = (b - a) / n;
x = a;
s = 0;
for (i = 1; i <= n; i++)
{
x = x + h;
s = s + (*p)(x)*h;
}
return(s);
}
float fsin(float x) //计算sin(x)的函数
{
return sin(x);
}
float fcos(float x) //计算cos(x)的函数
{
return cos(x);
}
float fexp(float x) //计算ex的函数
{
return exp(x);
} 运行结果：
//input a1, b1:0 1↙
//input a2, b2 : –1 1↙
//input a3, b3 : 0 2↙
//The integral of sin(x) is : 0.480639
//The integral of cos(x) is : 1.68154
//The integral of exp(x) is : 6.71383
14.将n个数按输入时顺序的逆序排列，用函数实现。
【解】
#include
using namespace std;
int main()
{
void sort(char *p, int m);
int i, n;
char *p, num[20];
cout << "input n:";
cin >> n;
cout << "please input these numbers:" << endl;
for (i = 0; i < n; i++)
cin >> num[i];
p = &num[0];
sort(p, n);
cout << "Now,the sequence is:" << endl;
for (i = 0; i < n; i++)
cout << num[i] << " ";
cout << endl;
return 0;
}
void sort(char *p, int m) //将n个数逆序排列函数
{
int i;
char temp, *p1, *p2;
for (i = 0; i < m / 2; i++)
{
p1 = p + i;
p2 = p + (m - 1 - i);
temp = *p1;
*p1 = *p2;
*p2 = temp;
}
} 运行结果：
//input n : 10↙
//please input these numbers :
//10 9 8 7 6 5 4 3 2 1↙
//Now, the sequence is :
//1 2 3 4 5 6 7 8 9 10
15.有一个班４个学生，5门课。①求第1门课的平均分；②找出有两门以上课程不及格的学生，输出他们的学号和全部课程成绩和平均成绩；③找出平均成绩在90分以上或全部课程成绩在85分以上的学生。分别编3个函数实现以上3个要求。
【解】
#include
using namespace std;
int main()
{
void avsco(float *, float *);
void avcour1(char(*)[10], float *);
void fail2(char course[5][10], int num[], float *psco, float aver[4]);
void good(char course[5][10], int num[4], float *psco, float aver[4]);
int i, j, *pnum, num[4];
float score[4][5], aver[4], *pscore, *paver;
char course[5][10], (*pcourse)[10];
cout << "input course:" << endl;
pcourse = course;
for (i = 0; i < 5; i++)
cin >> course[i];
cout << "input NO. and scores:" << endl;
cout << "NO.";
for (i = 0; i < 5; i++)
cout << "," << course[i];
cout << endl;
pscore = &score[0][0];
pnum = &num[0];
for (i = 0; i < 4; i++)
{
cin >> *(pnum + i);
for (j = 0; j < 5; j++)
cin >> *(pscore + 5 * i + j);
}
paver = &aver[0];
cout << endl << endl;
avsco(pscore, paver); //求出每个学生的平均成绩
avcour1(pcourse, pscore); //求出第一门课的平均成绩
cout << endl << endl;
fail2(pcourse, pnum, pscore, paver); //找出两门课不及格的学生
cout << endl << endl;
good(pcourse, pnum, pscore, paver); //找出成绩好的学生
return 0;
}
void avsco(float *pscore, float *paver) //求每个学生的平均成绩的函数
{
int i, j;
float sum, average;
for (i = 0; i < 4; i++)
{
sum = 0.0;
for (j = 0; j < 5; j++)
sum = sum + (*(pscore + 5 * i + j)); //累计每个学生的各科成绩
average = sum / 5; //计算平均成绩
*(paver + i) = average;
}
}
void avcour1(char(*pcourse)[10], float *pscore) //求第一课程的平均成绩的函数
{
int i;
float sum, average1;
sum = 0.0;
for (i = 0; i < 4; i++)
sum = sum + (*(pscore + 5 * i)); //累计每个学生的得分
average1 = sum / 4; //计算平均成绩
cout << "course 1: " << *pcourse << ",average score:" << average1 << endl;
}
void fail2(char course[5][10], int num[], float *pscore, float aver[4])
//找两门以上课程不及格的学生的函数
{
int i, j, k, labe1;
cout << " ==========Student who failed in two courses ======= " << endl;
cout << "NO. ";
for (i = 0; i < 5; i++)
cout << course[i] << " ";
cout << " average" << endl;
for (i = 0; i < 4; i++)
{
labe1 = 0;
for (j = 0; j < 5; j++)
if (*(pscore + 5 * i + j) < 60.0) labe1++;
if (labe1 >= 2)
{
cout << num[i] << " ";
for (k = 0; k < 5; k++)
cout << *(pscore + 5 * i + k) << " ";
cout << " " << aver[i] << endl;
}
}
}
void good(char course[5][10], int num[4], float *pscore, float aver[4])
//找成绩优秀的学生（全部课程成绩在85分以上或平均成绩在90分以上）的函数
{
int i, j, k, n;
cout << " ======Students whose score is good======" << endl;
cout << "NO. ";
for (i = 0; i < 5; i++)
cout << course[i] << " ";
cout << " average" << endl;
for (i = 0; i < 4; i++)
{
n = 0;
for (j = 0; j < 5; j++)
if (*(pscore + 5 * i + j) > 85.0) n++;
if ((n == 5) || (aver[i] >= 90))
{
cout << num[i] << " ";
for (k = 0; k < 5; k++)
cout << *(pscore + 5 * i + k) << " ";
cout << " " << aver[i] << endl;
}
}
} 运行结果：
//input course : （提示输入课程名称）
//English↙
//Computer↙
//Math↙
//Physics↙
//Chemistry↙
//input NO. and scores: （提示输入学号和各门课成绩）
//NO., English, Computer, Math, Physics, Chemistry, average （提示按此顺序输入）
//101 34 56 88 99 89↙
//102 77 88 99 67 78↙
//103 99 90 87 86 89↙
//104 78 89 99 56 77↙
//
//course 1: English, average score : 72 （第一门课英语的平均成绩为72）
//
//==========Students who failed in two courses====== = （有两门课不及格者）
//NO.English Computer Math Physics Chemistry average
//101 34 56 88 99 89 73.2
//
//======Student whose score is good====== （成绩优良者）
//NO.English Computer Math Physics Chemistry average
//103 99 90 87 86 89 90
16.输入一个字符串，内有数字和非数字字符，如将其中连续的数字作为一个整数，依次存放到一数组a中。例如，123放在a[0]，456放在a[1]……统计共有多少个整数，并输出这些数。
【解】
#include
using namespace std;
int main()
{
char str[50], *pstr;
int i, j, k, m, e10, digit, ndigit, a[10], *pa;
cout << "input a string:" << endl;
gets(str);
cout << endl;
pstr = &str[0]; //字符指针pstr指向数组str首元素
pa = &a[0]; //指针pa指向a数组首元素
ndigit = 0; //ndigit代表有多少个整数
i = 0; //i代表字符串中的第几个字符
j = 0; //j代表连续数字的位数
while (*(pstr + i) != '\0')
{
if ((*(pstr + i) >= '0') && (*(pstr + i) <= '9'))
j++;
else
{
if (j > 0)
{
digit = *(pstr + i - 1) - 48; //将个数位赋予digit
k = 1;
while (k < j) //将含有两位以上数的其他位的数值累计于digit
{
e10 = 1;
for (m = 1; m <= k; m++)
e10 = e10 * 10; //e10代表该位数所应乘的因子
digit = digit + (*(pstr + i - 1 - k) - 48)*e10; //将该位数累加于digit
k++; //位数k自增
}
*pa = digit; //将数值放在数组a中
ndigit++;
pa++; //指针pa指向a数组下一元素
j = 0;
}
}
i++;
}
if (j > 0) //以数字结尾字符串的最后一个数据
{
digit = *(pstr + i - 1) - 48; //将个数位赋予digit
k = 1;
while (k < j) //将含有两位以上数的其他位的数值累加于digit
{
e10 = 1;
for (m = 1; m <= k; m++)
e10 = e10 * 10; //e10代表位数所应乘的因子
digit = digit + (*(pstr + i - 1 - k) - 48)*e10; //将该位数的数值累加于digit
k++; //位数k自增
}
*pa = digit; //将数值放到数组a中
ndigit++;
j = 0;
}
printf("There are %d numbers in this line. They are:\n", ndigit);
j = 0;
pa = &a[0];
for (j = 0; j < ndigit; j++) //打印数据
cout << *(pa + j) << endl;
cout << endl;
return 0;
} 运行结果：
//input a string :
//a123x456 7689 + 89 = 321 / ab23↙
//There are 6 numbers in this line.They are :
//123 456 7689 89 321 23
17.写一函数，实现两个字符串的比较。即自己写一个strcmp函数，函数原型为int strcmp(char [^p1,char [^p2);设p1指向字符串s1，p2指向字符串s2。要求当s1=s2时，返回值为0，若s1≠s2，返回它们二者第1个不同字符的ASCII码差值（如"BOY"与"BAD"，第2个字母不同，"O"与"A"之差为79-65=14）。如果s1>s2，则输出正值，如s1
【解】
#include
using namespace std;
int main()
{
int strcmp(char *p1, char *p2);
int m;
char str1[20], str2[20], *p1, *p2;
cout << "input two strings:" << endl;
cin >> str1;
cin >> str2;
p1 = &str1[0];
p2 = &str2[0];
m = strcmp(p1, p2);
cout << "result:" << m << endl;
return 0;
}
int strcmp(char *p1, char *p2) //自己定义字符串比较函数
{
int i;
i = 0;
while (*(p1 + i) == *(p2 + i))
if (*(p1 + i++) == '\0') return(0); //全部字符相同时返回结果0
return(*(p1 + i) - (*(p2 + i))); //不相同时返回结果为第一对不相同字符的ASCII码的差值
}
运行结果：
//① input two strings :
//CHINA↙
//Chen↙
//result : - 32
//② input two strings :
//hello!↙
//hello!↙
//result : 0
//③ input two strings :
//dog↙
//cat↙
//result : 1
18.编写一程序，输入月份号，输出该月的英文月名。例如，输入3，则输出March，要求用指针数组处理。
【解】
#include
using namespace std;
int main()
{
char *month_name[13] = { "illegal month","January","February","March","April","May","June","July",
"August","September","October", "November","December" };
int n;
cout << "input month:" << endl;
cin >> n;
if ((n <= 12) && (n >= 1))
cout << "It is " << *(month_name + n) << endl;
else
cout << "It is wrong" << endl;
return 0;
}
运行结果：
//① input month : 2↙
//It is February.
//② input month : 8↙
//It is August.
//③ input month : 13↙
//It is wrong.
19.用指向指针的指针的方法对5个字符串排序并输出。
【解】
#include
using namespace std;
int main()
{
void sort(char **p);
const int m = 20; //定义字符串的最大长度
int i;
char **p, *pstr[5], str[5][m];
for (i = 0; i < 5; i++)
pstr[i] = str[i]; //将第i个字符串的首地址赋予指针数组 pstr 的第i个元素
cout << "input 5 strings:" << endl;
for (i = 0; i < 5; i++)
cin >> pstr[i];
p = pstr;
sort(p);
cout << "strings sorted:" << endl;
for (i = 0; i < 5; i++)
cout << pstr[i] << endl;
return 0;
}
void sort(char **p) //冒泡法对5个字符串排序函数
{
int i, j;
char *temp;
for (i = 0; i < 5; i++)
{
for (j = i + 1; j < 5; j++)
{
if (strcmp(*(p + i), *(p + j)) > 0) //比较后交换字符串地址
{
temp = *(p + i);
*(p + i) = *(p + j);
*(p + j) = temp;
}
}
}
}
运行结果：
//input 5 strings:
//China↙
//America↙
//India↙
//Philippines↙
//Canada↙
//strings sorted :
//America
//Canada
//China
//India
//Philippines
20.用指向指针的指针的方法对n个整数排序并输出。要求将排序单独写成一个函数。整数和n在主函数中输入。最后在主函数中输出。
【解】
#include
using namespace std;
int main()
{
void sort(int **p, int n);
int i, n, data[10], **p, *pstr[10];
cout << "input n:";
cin >> n;
for (i = 0; i < n; i++)
pstr[i] = &data[i]; //将第i个整数的地址赋予指针数组 pstr 的第i个元素
cout << "input " << n << " integer numbers:" << endl;
for (i = 0; i < n; i++)
cin >> *pstr[i];
p = pstr;
sort(p, n);
cout << "Now,the sequence is:" << endl;
for (i = 0; i < n; i++)
cout << *pstr[i] << " ";
cout << endl;
return 0;
}
void sort(int **p, int n)
{
int i, j, *temp;
for (i = 0; i < n - 1; i++)
{
for (j = i + 1; j < n; j++)
{
if (**(p + i) > **(p + j)) //比较后交换整数地址
{
temp = *(p + i);
*(p + i) = *(p + j);
*(p + j) = temp;
}
}
}
}
运行结果：
//input n : 7↙
//input 7 integer numbers :
//34 98 56 12 22 65 1↙
//Now, the sequence is :
//1 12 22 34 56 65 98
【解】
#include
using namespace std;
int main()
{
int strcmp(char *p1, char *p2);
int m;
char str1[20], str2[20], *p1, *p2;
cout << "input two strings:" << endl;
cin >> str1;
cin >> str2;
p1 = &str1[0];
p2 = &str2[0];
m = strcmp(p1, p2);
cout << "result:" << m << endl;
return 0;
}
int strcmp(char *p1, char *p2) //自己定义字符串比较函数
{
int i;
i = 0;
while (*(p1 + i) == *(p2 + i))
if (*(p1 + i++) == '\0') return(0); //全部字符相同时返回结果0
return(*(p1 + i) - (*(p2 + i))); //不相同时返回结果为第一对不相同字符的ASCII码的差值
} 运行结果：
//① input two strings :
//CHINA↙
//Chen↙
//result : - 32
//② input two strings :
//hello!↙
//hello!↙
//result : 0
//③ input two strings :
//dog↙
//cat↙
//result : 1
18.编写一程序，输入月份号，输出该月的英文月名。例如，输入3，则输出March，要求用指针数组处理。
【解】
#include
using namespace std;
int main()
{
char *month_name[13] = { "illegal month","January","February","March","April","May","June","July",
"August","September","October", "November","December" };
int n;
cout << "input month:" << endl;
cin >> n;
if ((n <= 12) && (n >= 1))
cout << "It is " << *(month_name + n) << endl;
else
cout << "It is wrong" << endl;
return 0;
} 运行结果：
//① input month : 2↙
//It is February.
//② input month : 8↙
//It is August.
//③ input month : 13↙
//It is wrong.
19.用指向指针的指针的方法对5个字符串排序并输出。
【解】
#include
using namespace std;
int main()
{
void sort(char **p);
const int m = 20; //定义字符串的最大长度
int i;
char **p, *pstr[5], str[5][m];
for (i = 0; i < 5; i++)
pstr[i] = str[i]; //将第i个字符串的首地址赋予指针数组 pstr 的第i个元素
cout << "input 5 strings:" << endl;
for (i = 0; i < 5; i++)
cin >> pstr[i];
p = pstr;
sort(p);
cout << "strings sorted:" << endl;
for (i = 0; i < 5; i++)
cout << pstr[i] << endl;
return 0;
}
void sort(char **p) //冒泡法对5个字符串排序函数
{
int i, j;
char *temp;
for (i = 0; i < 5; i++)
{
for (j = i + 1; j < 5; j++)
{
if (strcmp(*(p + i), *(p + j)) > 0) //比较后交换字符串地址
{
temp = *(p + i);
*(p + i) = *(p + j);
*(p + j) = temp;
}
}
}
} 运行结果：
//input 5 strings:
//China↙
//America↙
//India↙
//Philippines↙
//Canada↙
//strings sorted :
//America
//Canada
//China
//India
//Philippines
20.用指向指针的指针的方法对n个整数排序并输出。要求将排序单独写成一个函数。整数和n在主函数中输入。最后在主函数中输出。
【解】
#include
using namespace std;
int main()
{
void sort(int **p, int n);
int i, n, data[10], **p, *pstr[10];
cout << "input n:";
cin >> n;
for (i = 0; i < n; i++)
pstr[i] = &data[i]; //将第i个整数的地址赋予指针数组 pstr 的第i个元素
cout << "input " << n << " integer numbers:" << endl;
for (i = 0; i < n; i++)
cin >> *pstr[i];
p = pstr;
sort(p, n);
cout << "Now,the sequence is:" << endl;
for (i = 0; i < n; i++)
cout << *pstr[i] << " ";
cout << endl;
return 0;
}
void sort(int **p, int n)
{
int i, j, *temp;
for (i = 0; i < n - 1; i++)
{
for (j = i + 1; j < n; j++)
{
if (**(p + i) > **(p + j)) //比较后交换整数地址
{
temp = *(p + i);
*(p + i) = *(p + j);
*(p + j) = temp;
}
}
}
} 运行结果：
//input n : 7↙
//input 7 integer numbers :
//34 98 56 12 22 65 1↙
//Now, the sequence is :
//1 12 22 34 56 65 98