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：

 1 class Solution {
 2 public:
 3     /*
 4      * @param n: the integer to be reversed
 5      * @return: the reversed integer
 6      */
 7     int reverseInteger(int n) {
 8         long ret = 0;
 9         
10         while (n != 0) {
11             ret = ret * 10 + n % 10;
12             n /= 10;
13         }
14         
15         if (ret > INT_MAX || ret < INT_MIN) {
16             return 0;
17         }
18         
19         return (int)ret;
20     }
21 };

先用long来计算防止越界，然后再把越界的处理掉。

解法二：

 1 class Solution {
 2 public:
 3     int reverseInteger(int x) {
 4         int rst = 0;
 5         
 6         while(x != 0){
 7             int next_rst = rst * 10 + x % 10;
 8             x = x / 10;
 9             if(next_rst / 10 != rst) {
10                 rst  = 0;
11                 break;
12             }
13             rst = next_rst;
14         }
15         return rst;
16     }
17 };

参考@NineChapter 的代码