LeetCode 7. Reverse Integer

• Description
• Example
• Code
• Conclusion

Description

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

Example

Code

• java

class Solution {
    public int reverse(int x) {
        long temp = x, result = 0;
        boolean neg = x < 0 ? true : false;
        if(neg) temp = -temp;
        while(temp != 0) {
            result = result * 10 + temp % 10;
            temp /= 10;
        }
        long minValue = Integer.MAX_VALUE, maxValue = Integer.MAX_VALUE;
        minValue += 1;
        if((neg && result > minValue) || (!neg && result > maxValue)) return 0;
        if(neg) result = -result;
        return (int) result;
    }
}

• Official Solution

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;
    }
}

Conclusion

• 要特别注意边界情况，特别是负数