C language while structure classic exercises

while loop

- Compute the sum of positive integers

//计算用户规定范围内所有正整数之和
#include <stdio.h>

int main()
{
    
    
   int i=1,sum=0,n;
	printf("请输入终止范围\n");
	scanf("%d",&n);
	while(i<=n)
	{
    
    
		sum+=i;
		i++;
	}
	printf("sum=%d",sum);
   return 0;
}

operation result:

- calculate factorial

#include <stdio.h>
//(阶乘含义，5！=5*4*3*2*1 == 120)
int main()
{
    
    
   int i,sum=1;
	printf("请输入需要计算的阶乘\n");
	scanf("%d",&i);
	while(i>=1)
	{
    
    
		sum*=i;
		i--;
	}
	printf("sum=%d",sum);
   return 0;
}

operation result:

- Loop to read input data

#include <stdio.h>

int main()
{
    
    
	int n,sum=0;
	scanf("%d",&n);  //第一次获取，用于进行判断进入循环体（循环体外）
	while (n>=0)
	{
    
    
		sum+=n;
		scanf("%d",&n);  //第二次获取，用于进行用于循环读取输入的值（循环体外）
	}
	printf("sum=%d\n",sum);
   
   return 0;
}

operation result:

- Calculate the length of the input string

#include <stdio.h>

int main()
{
    
    
	char ch;
	int len=0;
	while ((ch=getchar())!= '\n')  //每次获取的字符只要不是回车（也是一个字符）就执行一次循环len则加一
		len++;
	printf("该字符串的长度为%d",len);
   
   return 0;
}

Calculation results:

- Add positive and negative numbers

#include <stdio.h>
//计算1-3+5-7+9
int main()
{
    
    
	int i=1,sum=0,k=1;
	while(i<=9)
	{
    
    
		sum+=i*k;
		i+=2;
		k=-k;   //也就是利用-1来控制正负，每次循环正负随之变化
	}
	printf("sum=%d",sum);
   
   return 0;
}

operation result:

- find the greatest common divisor

- more like subtractive method

#include <stdio.h>

int main()
{
    
    
	int a,b;
	scanf("%d%d",&a,&b);
	while (a!=b)    //注意条件为a不等于b
	{
    
    
		if (a>b) a-=b;  //大的减小的并赋值给原来大的
		if (b>a) b-=a;
	}
	printf("最大公约数为%d",a);
   return 0;
}

operation result:

- Roll and divide

#include <stdio.h>

int main()
{
    
    
	int a,b,t;
	scanf("%d%d",&a,&b);
	while (b!=0)    //注意条件为b不等于0
	{
    
    
		t=a%b;   //t为a对b求余，然后b赋值给a,t赋值给b
		a=b;
		b=t;
	}
	printf("最大公约数为%d",a);
   return 0;
}

operation result: