README.md

7. Reverse Integer

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

Example 1:

Input: 123
Output: 321

Example 2:

Input: -123
Output: -321

Example 3:

Input: 120
Output: 21

Note:

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.

Solutions (Python)

1. Pop & Push Digits

class Solution:
    def reverse(self, x: int) -> int:
        result = 0
        xc = abs(x)
        while xc != 0:
            result *= 10
            result += xc % 10
            xc //= 10
        if result < -(2 ** 31) or result > (2 ** 31) - 1:
            return 0
        elif x >= 0:
            return result
        else:
            return -result

Solutions (C)

int reverse(int x)
{
    int Int_Max = 0x7fffffff;
    int Int_Min = 0x80000000;
    long sum = 0;  
    for( ; x; x /= 10 )
       sum = ( sum *= 10 ) + x % 10; 
    if( sum > Int_Max || sum < Int_Min )
        return 0;
    return sum;
}