判断一个正整数有几位

while语句：先判断条件，再执行循环体。 

# include<stdio.h>

int main()
{
    int x;
    int n = 0;
    
    scanf("%d", &x);
    
    x/=10;
    n++;
    
    while(x>0){
        
        x/=10;
        n++;
        
    }
    
    printf("%d\n", n);
    
    return 0;
}

do while语句：先执行循环体，再判断条件是否满足。

 

# include<stdio.h>

int main()
{
    int x;
    int n = 0;
    
    scanf("%d", &x);
    
    do{
        x/=10;
        n++;
    }while(x>0);
    
    printf("%d\n", n);
    
    return 0;
}