413. Reverse Integer【easy】

Reverse digits of an integer. Returns 0 when the reversed integer overflows (signed 32-bit integer).

 

Example

Given x = 123, return 321

Given x = -123, return -321

解法一：

class Solution {
public:
    /*
     * @param n: the integer to be reversed
     * @return: the reversed integer
     */
    int reverseInteger(int n) {
        long ret = 0;
        
        while (n != 0) {
            ret = ret * 10 + n % 10;
            n /= 10;
        }
        
        if (ret > INT_MAX || ret < INT_MIN) {
            return 0;
        }
        
        return (int)ret;
    }
};

先用long来计算防止越界，然后再把越界的处理掉。

解法二：

class Solution {
public:
    int reverseInteger(int x) {
        int rst = 0;
        
        while(x != 0){
            int next_rst = rst * 10 + x % 10;
            x = x / 10;
            if(next_rst / 10 != rst) {
                rst  = 0;
                break;
            }
            rst = next_rst;
        }
        return rst;
    }
};

参考@NineChapter 的代码