50道C/C++编程练习题 复习必备(21-30)

使用C/C++两种语言完成50道题目，体会两种语言之间的不同。编译环境都是在VS2019，完成时间2020.06.21-2020.06.22 。由于C++ 对C的兼容性，部分main()函数没有写return 0 也可以执行成功，但是不提倡,最好加上，否则其他编译器可能报错。C语言不需要严格对齐，因此不对CSDN 的格式做过多的纠正。

21. 写一个函数，将一个整数的各位数字的反序打印

C

#include
int rev(int k);
int main()
{
 int k = 234;
 rev(k);
}
int rev(int k)
{
 int z;
 while (k > 0)
 {
  z = k % 10;
  printf(" %d",z);
  k = k / 10;
 }
 return 0;
}

C++

#include
using namespace std;
int rev(int k);
int main()
{
 int k = 234;
 rev(k);
}
int rev(int k)
{
 int z;
 while(k>0)
 {
  z = k % 10;
  cout << z << " ";
  k = k / 10;
 }
 return 0;
}

22. 写一个函数，将一个整数的各位数字的按顺序打印出来

C

#include
int show(int);
int main()
{
 int n = 7990;
 show(n);
}
int show(int n)
{
 int m = n;
 int i = 0;
 int k = 1;
 int s;
 while (m > 0)
 {
  i = i + 1;
  m = m / 10;
  //cout << "i==" << i;
 }
 for (int j = 1; j < i; j++)
  k = k * 10;      //从最大值开始除
 while (k > 0)
 {
  s = n / k;
  printf(" %d",s);
  n = n % k;
  k = k / 10;
 }
 return 0;
}

C++

#include

using namespace std;
int show(int);
int main()
{
 int n = 7990;
 show(n);
}
int show(int n)
{ 
 int m = n;
 int i = 0;
 int k = 1;
 int s;
 while (m>0)
 {
  i = i + 1;
  m = m / 10;
  //cout << "i==" << i;
 }
 for (int j = 1; j <  i; j++)
  k = k * 10;      //从最大值开始除
 //cout << " k==" << k<
 while(k>0)
 {
  s = n / k;
  
  cout << " "<<s;
  n = n %k;
  k = k / 10;
 }
 return 0;
}

23. 求一个整数的各位数之和的函数

C

#include
int sum(int);
int main()
{
 int z;
 int n = 345;
 z = sum(n);
 printf("%d",z);
}
int sum(int n)
{
 int s = 0;
 while (n)
 {
  s += n % 10;
  n /= 10;
 };
 return s;
}

C++

#include
using namespace std;
int sum(int);
int main()
{
 int z;
 int n = 345;
 z = sum(n);
 cout<<z;
}
int sum(int n)
{
 int s = 0;
 while (n)
 {
  s += n % 10;
  n /= 10;
 };
 return s;
}

24. 写一函数，判断某个数是否素数，以及求1－1000之内的素数

C

#include
#include
bool isprime(int);
int main()
{
 for (int i = 2; i <= 1000; i++)
 {
  if (isprime(i))
      printf(" %d",i);
 }
 return 0;
}
bool isprime(int k)
{
 float m;
 m = sqrt(float(k));
 for (int i = 2; i <= m; i++)
 {
  if (k % i == 0)
      return false;
 }
 return true;
}

C++

#include
#include
using namespace std;
bool isprime(int);
int main() 
{
 for(int i=2;i<=1000;i++)
 {
  if (isprime(i))
   cout << " " << i;
 }
}
bool isprime(int k)
{
 float m;
 m = sqrt(float(k));
 for (int i = 2; i <= m; i++)
 {
  if (k % i == 0)
   return false;
 }
 return true;
}

25. 用筛法求1－1000之内的素数

#include 
#include 
#include 
#include 
using namespace std;
int main()
{
 int i, k, a[1001];
 for (i = 2; i <= 1000; i++) a[i] = 1;
 float s = sqrt(float(1000));
 for (i = 2; i <= s; i++)
  if (a[i] == 1)
  {
   k = 2 * i;
   while (k <= 1000)
   {
    a[k] = 0;
    k = k + i;
   }
  }
 for (i = 2; i <= 1000; i++)
  if (a[i] == 1) cout << setw(5) << i;
}

26. 判断某一年是否闰年的函数

C

#include
bool IsLeapYear(int);
int main()
{
 int y = 2008;
 bool z = IsLeapYear(y);
 printf("%d",z);
}
bool IsLeapYear(int y)
{
 return (y % 4 == 0 && y % 100 != 0) || (y % 400 == 0);
}

C++

#include
using namespace std;
bool IsLeapYear(int);
int main()
{
 int y = 2008;
 bool z = IsLeapYear(y);
 cout << z;
}
bool IsLeapYear(int y)
{
 return (y % 4 == 0 && y % 100 != 0) || (y % 400 == 0);
}

27、写一个函数，交换两个整型变量的值

C

#include
void swap(int*, int*);
void swap(int& a, int& b)
{
 int t;
 t = a; a = b; b = t;
}
int main()
{
 int a = 3, b = 5;
 swap(a, b);
 printf("%d  %d",a,b);
}

C++

#include
using namespace std;
void swap(int*, int*);
void swap(int& a, int& b)
{
 int t;
 t = a; a = b; b = t;
}
int main()
{
 int a = 3, b = 5;
 swap(a, b);
 cout << a <<"  "<< b;
}

28. 求两个数的最大公约数,欧几里德算法(辗转相除法）

C

#include
int gcd(int, int);
int main()
{
 int a = 45, b = 90;
 int z;
 a > b ? z = gcd(a, b) : z = gcd(b, a);
 printf("%d",z);
}
int gcd(int a, int b)
{
 int r = a % b;
 if (r == 0) return b;
 else
  return gcd(b, r);
}

C++

#include
using namespace std;
int gcd(int, int);
int main()
{
 int a = 45, b = 90;
 int z;
 a > b ? z=gcd(a, b) : z=gcd(b, a);
 cout << z;
}
int gcd(int a,int b)
{
 int r = a % b;
 if (r == 0) return b;
 else
  return gcd(b, r);
}

29. 求两个数的最小公倍数

C

#include
int gcd(int, int);
int main()
{
 int a = 45, b = 25;
 int z;
 a > b ? z = gcd(a, b) : z = gcd(b, a);
 printf("%d", a*b/z);
}
int gcd(int a, int b)
{
 int r = a % b;
 if (r == 0) return b;
 else
  return gcd(b, r);
}

C++

#include
using namespace std;
int gcd(int, int);
int main()
{
 int a = 45, b = 25;
 int z;
 a > b ? z=gcd(a, b) : z=gcd(b, a);
 cout << a*b/z;
}
int gcd(int a,int b)
{
 int r = a % b;
 if (r == 0) return b;
 else
  return gcd(b, r);
}

30. 百钱买百鸡问题：鸡翁一值钱五，鸡母一值钱三，鸡雏三值钱一，百钱买百鸡，问鸡翁、母、雏各几何？

C

#include
using namespace std;
int main()
{
 for (int a = 0; a <= 20; a++)
  for (int b = 0; b <= 33; b++)
   for (int c = 0; c <= 100 - a - b; c = c + 3)
    if ((a + b + c == 100) and (5 * a + 3 * b + c / 3 == 100))
     printf("%d %d %d \n",a,b,c); 
}

C++

#include
using namespace std;
int main()
{
 for (int a = 0; a <= 20; a++)
  for (int b = 0; b <= 33; b++)
   for (int c = 0; c <= 100 - a - b; c = c + 3)
    if ((a + b + c == 100) and (5 * a + 3 * b + c / 3 == 100))
     cout << a << " "<<b<<" " << c<<endl;
}