Problem 7 Reverse Integer

Language

JavaScript Java

Description

Given a 32-bit signed integer, reverse digits of an integer.

Example

Input

1. 123
2. -123
3. 123

Output

1. 321
2. -321
3. 21

Explanation

Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−231,  231 − 1]. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.

Analysis

The biggest problem is to prevent overflow, so we check the origin x and the answer ans. If they're bigger than 2^31-1, print 0 directly.
Besides, we reverse the number x by read and traverse as string reversed.

Solution

JavaScript

/**
 * @param {number} x
 * @return {number}
 */
var reverse = function(x) {
    if(x === 0) return 0;
    Math.abs(x)>(2**31-1)?x=0:x;
    let ans='';
    let rev = Math.abs(x).toString();
    for(var i =0;i<rev.length;i++){
        ans += rev[rev.length-i-1]
    }
    return parseInt(Math.abs(ans)>(2**31-1)?len=0:(x<0?-ans:ans));
};

Java

class Solution {
    public int reverse(int x) {
         long rev= 0;
        while( x != 0){
            rev= rev*10 + x % 10;
            x= x/10;
            if( rev > Integer.MAX_VALUE || rev < Integer.MIN_VALUE)
                return 0;
        }
        return (int) rev;

    }
}