leetcode - 7. Reverse Integer

Degree

Easy ★ (*´╰╯`๓)♬

Description:

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

Note:

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

Example1:

Input: 123
Output:  321

Example2:

Input: -123
Output: -321

Example3:

Input: 120
Output: 21

Ideas

• 模十法，将各位的数字依次往最高位升
• 初始为负数的依然为负数形式
• 当数字大小茶超过2^32的时候，就返回0

Code

var reverse = function(x) {
    var y = Math.abs(x);
    var result = 0;
    while(y > 0){
        result = result * 10 + y % 10;
        y = parseInt(y / 10);
    }
    result = x < 0 ? -result : result;
    return result >= -Math.pow(2,31) && result <= Math.pow(2,31) - 1 ? result : 0;
};