[Leetcode]-Reverse Integer

Posted 2020-09-24 liguangsunls

//假设有pow函数，Linux下编译一定要加-lm
//gcc ReverseInteger.c -o ReverseInteger -lm
关键：一定要注意操作过程中int类型超界
有可能输入数据没有超界。可是反向逆序后，甚至在逆序操作过程中都有可能超界。反正时刻检查超界与否

#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <limits.h>

int reverse(int x) {
    int f = 0;
    int k = 0;
    int m = 0;
    int tem=0;
    int r = 0;
    int INT_MAX_DIV10 = INT_MAX / 10;
    if(x<-INT_MAX && x >INT_MAX) 
        return 0;

    if(x < 0) 
    {
        x = -x;
        f = 1;
    }
    while(x)
    {   
        if(r > INT_MAX_DIV10) return 0;
        r = r*10;
        tem = x % 10;
        if(INT_MAX - tem < r) return 0;
        r = r + tem;
        x = x/10;
    }
    if(f)
        r = -r;

    return r;
}

int main()
{
    int x = 1;
    int r = reverse(x);
    printf("reverse x %d = %d \n",x,r);

    x = 13579;
    r = reverse(x);
    printf("reverse x %d = %d \n",x,r);

    x = 0;
    r = reverse(x);
    printf("reverse x %d = %d \n",x,r);

    x = -13579;
    r = reverse(x);
    printf("reverse x %d = %d \n",x,r);

    x = -1;
    r = reverse(x);
    printf("reverse x %d = %d \n",x,r);

    x = 1534236469; //原数不超界。逆序超界
    r = reverse(x);
    printf("reverse x %d = %d \n",x,r);
}