7. Reverse Integer

难度: Medium

题目描述

Given a signed 32-bit integer x, return x with its digits reversed. If reversing x causes the value to go outside the signed 32-bit integer range [-231, 231 - 1], then return 0.

Assume the environment does not allow you to store 64-bit integers (signed or unsigned).

 

Example 1:

Input: x = 123
Output: 321

Example 2:

Input: x = -123
Output: -321

Example 3:

Input: x = 120
Output: 21

 

Constraints:

• -231 <= x <= 231 - 1

解题思路

代码实现

解决方案

java

class Solution {
    public int reverse(int x) {
        
        if (x > Integer.MAX_VALUE || x< Integer.MIN_VALUE) {
            return 0;
        }
        long temp =x;
        boolean flag = false;
        if (temp < 0) {
            flag = true;
            temp = Math.abs(temp);
        }

        StringBuilder sb = new StringBuilder(temp+"");
        sb.reverse();
        Long l = Long.parseLong(sb.toString());

        if (l > Integer.MAX_VALUE || (flag && l < Integer.MIN_VALUE)) {
            return 0;
        }
        if(flag){
            return  0-l.intValue();
        }
        return l.intValue();
    }
}