7. Reverse Integer Leetcode Solution in JavaScript (JS)

Problem

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

Solution

Time Complexity O(n)

/**
 * @param {number} x
 * @return {number}
 */
var reverse = function(x) {
    if(x > 2147483647 || x < -2147483647){
        return 0;
    }
    if(reversestring(x) > 2147483647 || reversestring(x) < -2147483647){
        return 0;
    }
   return reversestring(x);
};
function reversestring(x){
    x = x.toString();
    x = x.split("");
    let isminus = "";
    if(x[0] == "-"){
        x.shift();
        isminus = "-";
    }
    let output = "";
 
    for(let i = x.length -1; i >= 0; i--){
            
            output = output+x[i];
    }
   
    return isminus+output;
}