Problem #7: Reverse Integer

Intuition & Strategy Breakdown

Extract digits from right to left using modulo 10 and construct the reversed integer. Before multiplying by 10, check for 32-bit signed integer overflow bounds [-2^31, 2^31 - 1].

Python Solution

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

Java Solution

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