007_Reverse_Integer.java

// 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.
//


class Solution {
    public int reverse(int x) {
            int rev = 0;
        while (x != 0) {
            int pop = x % 10;
            x /= 10;
            if (rev > Integer.MAX_VALUE/10 || (rev == Integer.MAX_VALUE / 10 && pop > 7)) return 0;
            if (rev < Integer.MIN_VALUE/10 || (rev == Integer.MIN_VALUE / 10 && pop < -8)) return 0;
            rev = rev * 10 + pop;
        }
        return rev;
    }
}