复制代码 代码如下:

# include <stdio.h>
int main(void)
{
int m,val,sum = 0;
printf("请输入一个回文数，如果是回文数返回YES，否则返回No：");
scanf("%d",&val);
m = val;
while(m)
{
sum = sum*10+m%10;
m/= 10;
}
if(sum == val)
printf("YES\n");
else
printf("NO\n");

}

//对while语句进行流程分析
//假设用户输入数字121，判断是否回文数，m非0是真，否则为假，为真输出YES，假输出No；

1--->sum = sum*10+m%10 (sum = 0*10+121%10)//sum=0+1，sum=1
m / = 10（m=m/10）//m=121/10，m=12
2--->sum = sum*10+m%10(sum=1*10+12%10)//sum=10+2，sum=12
m / 10 =10(m=m/10) //m=12/10，m=1
3--->sum = sum*10+m%10(sum=12*10+1%10)//sum=120+1，sum=121
m / 10 =10(m=m/10) //m=1/10，m=0

m = 0为假，则输出No