Why 1534236469 can't pass [closed]

Question

I think 1534236469 out of range! Leetcode: 7. Reverse Integer I can't pass the test input 1534236469. why? the return range is[Integer.MAX_VALUE, Integer.MIN_VALUE],others should return zero

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

Thank for your help

Answer 1

The reverse of 1534236469 is 9646324351, which is larger than Integer.MAX_VALUE, so your code will result in numeric overflow and an incorrect result.

You can use long instead of int to fix the problem.

EDIT:

Your added if(x > Integer.MAX_VALUE || x < Integer.MIN_VALUE) condition is pointless, since x is int, so it will never be outside the valid range of ints.

Even if x is within the valid range, the reverse of x may be outside the range. If you want to detect that the reversed x is too large and return 0, you should use long internally:

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