LeetCode - E - Reverse Integer

題意

Reverse digits of an integer.

Example1: x = 123, return 321
Example2: x = -123, return -321

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Note:
The input is assumed to be a 32-bit signed integer. Your function should return 0 when the reversed integer overflows.

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解法

注意溢出問題

實現

class Solution {
public:
    int reverse(int x) {
        long long y = x;
        if(x < 0) y = y * -1;//注意用long long類型代替int
        long long reverse = 0;
        long long max = 2147483647;
        while(y != 0){
            reverse = reverse * 10 + y % 10;
            if((x > 0 && reverse > max) || (x < 0 && reverse > max + 1)) return 0;
            y = y / 10;
        }
        if(x < 0) reverse = reverse * -1;
        return reverse;
    }
};