计算自然数之和的三种方法

1.使用for

#include
int main()
{int n,i,sum;//声明变量sum = 0;//定义初值printf(" 请输入正整数：");scanf("%d",&n);for (i = 0; i <=n;i++){sum += i;}printf("sum=%d", sum);return 0;
}

2使用while

#include
int main()
{int n,i,sum;//声明变量sum = 0;//定义初值i = 1;printf(" 请输入正整数：");scanf("%d",&n);while(i<=n){sum += i;++i;}printf("sum=%d", sum);return 0;
}

3.使用递归

#include
int addnumbers(int n);//声明求和函数
int main()
{int num,sum;//声明变量sum = 0;//定义初值printf(" 请输入正整数：");scanf("%d",&num);printf("sum=%d",addnumbers(num));return 0;
}
int addnumbers(int n)
{if (n != 0)return n=addnumbers(n - 1);elsereturn n;
}