C PRIMER PLUS第六版 第十一章编程练习

1.

#include 
#define SIZE 40
void s_gets(char str[], int n);

int main(void)
{
    int i;
    int num;
    char st [SIZE];

    printf("Enter a number for the length of the string:");
    scanf("%d",&num);
    while(getchar() != '\n')
        continue;
    s_gets(st,num);
    fputs(st,stdout);
    printf("\n");
    for (i = 0; i < num; ++i) {
        printf("%d\n",st[i]);
    }

    return 0;
}

void s_gets(char str[], int n)
{
    printf("Enter a string:");
    fgets(str,n,stdin);
}

 

2.

    #include 
    #include 
    #define SIZE 40
    void s_gets(char str[], int n);

    int main(void)
    {
        int i;
        int num;
        char st [SIZE];

        printf("Enter a number for the length of the string:");
        scanf("%d",&num);
        while(getchar() != '\n')
            continue;
        s_gets(st,num);
        puts(st);
        printf("\n");
        for (i = 0; i < num; i++) {
            printf("%d\n",st[i]);
        }

        return 0;
    }

    void s_gets(char str[], int n)
    {
        int i;
        printf("Enter a string:");
        for (i = 0; i < n; i++) {
            str[i] = getchar();
            if(isspace(str[i])) {
                str[i] = '\0';
                break;
            }
        }
    }

 

3.

#include 
#include 
#include 
#define SIZE 80
void s_gets(char * st);

int main(void)
{
    char str [SIZE];
    int length;
    int i;

    printf("Enter a string, we will get the first word:");
    s_gets(str);
    length = strlen(str);
    for(i = 0; i < length; i++)
        printf("%c",str[i]);

    return 0;
}

void s_gets(char * st)
{
    int i = 0;
    int j;

    while(isspace(st[i] = getchar()))
        continue;
    for(j = 1; ; j++)
    {
        st[j] = getchar();
        if(isspace(st[j]))
        {
            st[j] = '\0';
            break;
        }
    }
}

 

4.

#include 
#include 
#include 
#define SIZE 80
void s_gets(char * st, int n);

int main(void)
{
    char str [SIZE];
    int length;
    int i,max;

    printf("Enter the up limit of the letters in the word:");
    scanf("%d",&max);
    printf("Enter a string, we will get the first word:");
    s_gets(str,max);
    length = strlen(str);
    for(i = 0; i < length; i++)
        printf("%c",str[i]);

    return 0;
}

void s_gets(char * st, int n)
{
    int i = 0;
    int j;

    while(isspace(st[i] = getchar()))
        continue;
    for(j = 1; j < n; j++)
    {
        st[j] = getchar();
        if(isspace(st[j]))
        {
            st[j] = '\0';
            break;
        }
    }
}

 

5.

#include 
#include 
#define SIZE 80
char * select(char * st, const char ch);

int main(void)
{
    char str[SIZE];
    char target;
    char * ans;

    printf("Enter a srting(less than 80 letters):");
    fgets(str,SIZE,stdin);
    printf("Enter the character you want to find in the string:");
    scanf("%c",&target);
    ans = select(str,target);

    if(ans == NULL)
        printf("No character has been found.\n");
    else
        printf("The character is at the location of str[%d].",ans - str);

    return 0;
}

char * select(char * st, const char ch)
{
    char * ret;
    int i,s;
    s = strlen(st);
    for(i = 0; i < s; i++)
    {
        if(st[i] == ch)
        {
            ret = &st[i];
            return ret;
        }
    }
    return NULL;
}

 

6.

#include 
#include 
#define SIZE 80
int is_within(char ch, char * st);

int main(void)
{
    char str [SIZE];
    char target;
    int i;

    printf("Enter the character you want to find in the string(# to quit):");
    scanf("%c",&target);
    getchar();
    while(target != '#')
    {
        printf("Enter a srting(less than 80 letters):");
        fgets(str,SIZE,stdin);
        i = is_within(target, str);
        if(i)
            printf("We find the character in the string!\n");
        else
            printf("Nothing has been found.\n");
        printf("Enter next character you want to find(# to quit):");
        scanf("%c",&target);
        getchar();
    }
    printf("bye!");

    return 0;
}

int is_within(char ch, char * st)
{
    int ret;
    if(strchr(st,ch))
        ret = 1;
    else
        ret = 0;

    return ret;
}

 

7.

#include 
#include 
#define SIZE_OF_SOU 100
#define SIZE_OF_COPY 40
#define SIZE 20
char * mystrncpy(char * s1, char * s2, int n);

int main(void)
{
    char sou[SIZE_OF_SOU];
    char copy[SIZE_OF_COPY];
    int i,l;
    i = 0;

    printf("Enter the source string(press Enter to quit):");
    gets(sou);
    while(sou[0] != '\0')
    {
        printf("Enter the second string you want to copy to source:");
        gets(copy);
        printf("Enter the length of copy:");
        scanf("%d",&l);
        getchar();
        mystrncpy(sou, copy, l);
        printf("Now the source string is:\n");
        puts(sou);
        while(sou[i])
        {
            sou[i] = '\0';
            i++;
        }
        printf("Enter the source string(press Enter to quit):");
        gets(sou);
    }
    printf("bye\n");

    return 0;
}

char * mystrncpy(char * s1, char * s2, int n)
{
    int i,len;

    len = strlen(s1);
    for(i = 0; i < n; i++)
        s1[len+i] = s2[i];

    return s1;
}

 

8.

#include 
#include 
#define SIZE 80
char * string_in(char * s1, char * s2);

int main(void)
{
    char sou[SIZE];
    char in[SIZE];
    char * start;
    int i = 0;

    printf("Enter the source string(press Enter to quit):");
    gets(sou);
    while(sou[0] != '\0')
    {
        printf("Enter the string that is in the source string:");
        gets(in);
        start = string_in(sou,in);
        if(start)
            printf("The string is in the source string beginning at sou[%d].\n",start - sou);
        else
            printf("No string has been found in the source string.\n");
        while(sou[i])
        {
            sou[i] = '\0';
            i++;
        }
        printf("Enter the source string(press Enter to quit):");
        gets(sou);
        }
        printf("bye");

    return 0;
}

char * string_in(char * s1, char * s2)
{
    int i;
    int len_1,len_2;

    len_1 = strlen(s1);
    len_2 = strlen(s2);
    for(i = 0; i < (len_1 - 1 - len_2); i++)
    {
        if(strncmp(s1+i, s2, len_2) == 0)
        {
            return (s1+i);
        }
    }
    return NULL;
}

 

9.

#include 
#include 
#define SIZE 80
char * sort(char * st);

int main(void)
{
    char sou[SIZE];
    int i;

    printf("Enter a string, I will sort it for you(press enter to quit):");
    gets(sou);
    while(sou[0] != '\0')
    {
        sort(sou);
        puts(sou);
        while(sou[i])  //用来清空sou数组中的元素，从而判断循环条件
        {
            sou[i] = '\0';
            i++;
        }
            printf("Enter a string, I will sort it for you(press enter to quit):");
        gets(sou);
    }
    printf("bye\n");

    return 0;
}

char * sort(char * st)
{
    int i;
    int len;
    char temp;

    len = strlen(st);
    for(i = 0; i < len / 2; i++)
    {
        temp = st[i];
        st[i] = st[len - i - 1];
        st[len - i - 1] = temp;
    }
    return st;
}

 

10.

#include 
#include 
#include 
#define SIZE 100
char * delblk(char * st);

int main(void)
{
    char sou[SIZE];
    int i = 0;

    printf("Enter a string, I will delete the blanks for you(Press enter to quit):");
    gets(sou);
    while(sou[0] != '\0')
    {
        delblk(sou);
        fputs(sou,stdout);
        printf("\n");
        while(sou[i] != '\0')
        {
            sou[i] = '\0';
            i++;
        }
        printf("Enter a string, I will delete the blanks for you(Press enter to quit):");
        gets(sou);
    }
    printf("bye\n");

    return 0;
}

char * delblk(char * st)
{
    int i,j;
    int len,tlen;
    char temp[SIZE];
    i = j = 0;

    len = strlen(st);
    while(i < len)
    {
        if(isspace(st[i]))
        {
            i++;
            continue;
        }
        else
        {
            temp[j] = st[i];
            i++;
            j++;
        }
    }
    i = 0;
    while(st[i] != '\0')  //清空st数组，以便下面重新赋值
    {
        st[i] = '\0';
        i++;
    }
    tlen = strlen(temp);
    for(i = 0; i < tlen; i++)
        st[i] = temp[i]; //如果上面没有清空st数组，那么在赋值的时候只有前一部分元素赋值，后面未赋值的元素任然存在，所以会输出有问题
    return st; //上面一部分也可以不要，但是这里如果返回temp的话，会被提示local variable的错误，局部变量在这里用完后是会被释放的，所以重新赋值st，具体原因到后面学习。
    }

 

11.

#include 
#include 
#include 
#define SIZE 100

void print(char * st);
void print_asc(char * st);
void print_up(char * st);
void print_first_length(char * st);
char *s_gets(char * st, int n);

int main(void)
{
    char source[SIZE];
    char choice;

    printf("请输入一串英文字符（不超过80个英文字符）：");
    s_gets(source,10);
    printf("----------------------------------------\n");
    printf("|         请选择你想做的事：              |\n");
    printf("|  a.顺序打印字符       b.打印ASCII码     |\n");
    printf("|  c.长度递增打印       d.第一个单词长度打印|\n");
    printf("|             q.不玩了                  |\n");
    printf("----------------------------------------\n");
    scanf("%c",&choice);
    getchar();

    while(choice != 'q')
    {
        switch(choice)
        {
            case 'a':
                print(source);
                break;
            case 'b':
                print_asc(source);
                break;
            case 'c':
                print_up(source);
                break;
            case 'd':
                print_first_length(source);
                break;
            default:
                printf("请输入正确选项：");
                scanf("%c",&choice);
                getchar();
                continue;
        }
        printf("----------------------------------------\n");
        printf("|         请选择你想做的事：              |\n");
        printf("|  a.顺序打印字符       b.打印ASCII码     |\n");
        printf("|  c.长度递增打印       d.第一个单词长度打印|\n");
        printf("|             q.不玩了                  |\n");
        printf("----------------------------------------\n");
        scanf("%c",&choice);
        getchar();
    }
    printf("再见");

    return 0;
}

void print(char * st)
{
    printf("你的字符串是：\n");
    puts(st);
}

void print_asc(char * st)
{
    int i;
    int len;

    len = strlen(st);
    printf("下面将打印你所输入字符串的ASCII码:\n");
    for(i = 0; i < len; i++)
        printf("%d ",st[i]);
    printf("\n");
}

void print_up(char * st)
{
    int i,j;
    int len;

    len = strlen(st);
    printf("下面将按递增顺序打印字符串字符：\n");
    for(i = 0; i < len; i++)
    {
        for(j = 0; j <= i; j++)
            printf("%c",st[j]);
        printf("\n");
    }
}

void print_first_length(char * st)
{
    int i,j;
    int len;

    len = strlen(st);
    printf("下面将根据你第一个单词的长度打印字符串：\n");
    for(i = 0; i < len; i++)
    {
        if(isspace(st[i]))
            continue;
        else
        {
            for(j = i; j < len; j++)
                if(isspace(st[j]))
                {
                    st[j] = '\0';
                    break;
                }
            break;
        }
    }
    puts(st);
}

char *s_gets(char * st, int n)
{
    char * ret_val;
    int i = 0;

    ret_val = fgets(st,n,stdin);
    if (ret_val)
    {
        while(st[i] != '\n' && st[i] != '\0')
            i++;
        if (st[i] == '\n')
            st[i] = '\0';
        else
            while(getchar() != '\n');
    }

    return ret_val;
}

 

12.

#include 
#include 
#include 
#define  SIZE 100

int main(void)
{
    char source[SIZE];
    int top_words,low_words,words,puncs,nums;
    int i;
    int len;
    top_words = low_words = words = puncs = nums = 0;

    printf("Enter a string:");
    fgets(source, SIZE, stdin);
    len = strlen(source);
    for(i = 0; i < len ; i++)
    {
        if(isalpha(source[i]))
        {
            if(source[i] >= 'a' && source[i] <= 'z')
                low_words++;
            else
                top_words++;
            words++;
        }
        else if(ispunct(source[i]))
            puncs++;
        else if(isdigit(source[i]))
            nums++;
    }
    printf("There are totally %d words, including %d uppers and %d lowers, %d punctuals and %d numbers.\n",words,top_words,low_words,puncs,nums);
    printf("That's over!");

    return 0;
}

 

13.

#include 

int main(int argc,char *argv[])
{
    int i;

    for(i = 1; i < argc; i++)
        printf("%s ",argv[argc-i]);

    return 0;
}

 

14.

#include 
#include 

int main(int argc, char ** argv)
{
    double base;
    int index;
    double ans = 1;
    int i;

    base = atof(argv[1]);
    index = atoi(argv[2]);

    for(i = 0; i < index; i++)
        ans *= base;
    printf("The result is %lf",ans);

    return 0;
}

 

15.

#include 
#include 
#include 
#include 
#define SIZE 100
double atoi(char * st);

int main(void)
{
    char num[SIZE];
    double retu;

    printf("Enter a string including numbers:");
    gets(num);
    retu = atoi(num);
    printf("%lf\n",retu);

    return 0;
}

double atoi(char * st)
{
    int i;
    int len;
    double result = 0;
    len = strlen(st);

    for(i = 0; i < len; i++)
    {
        if(isdigit(st[i]))
        {
            result += ((st[i]-'0')*pow(10,(len-i-1)));
        }

        else
            return 0;
    }
    return result;
}

 

16.

#include 
#include 
#include 
#define SIZE 80

int main(int argc, char **argv)
{
    char source[SIZE];
    int i;
    int len;

    printf("Enter a string:");
    fgets(source, SIZE, stdin);
    len = strlen(source);

    if(strcmp(argv[1],"-u") == 0) //这个地方不能直接判断argv[1] == "-u"，如果这样写，那么比较的是字符串的地址，而不是字符串本身
    {
        for(i = 0; i < len; i++)
            source[i] = toupper(source[i]);
        fputs(source,stdout);
    }
    else if(strcmp(argv[1],"-l") == 0)
    {
        for(i = 0; i < len; i++)
            source[i] = tolower(source[i]);
        fputs(source,stdout);
    }
    else
        fputs(source,stdout);

    return 0;
}