# LeetCode - 1927. Sum Game
### 題目網址：https://leetcode.com/problems/sum-game/
###### tags: `LeetCode` `Medium` `數學`

/*
    -LeetCode format-
    Problem: 1927. Sum Game
    Difficulty: Medium
    
    by Inversionpeter
*/



static const auto Initialize = []{
    ios::sync_with_stdio(false); cin.tie(nullptr);
    return nullptr;
}();

class Solution {
public:
    bool sumGame(string num) {
        int half = num.size() >> 1, blanks = 0, difference = 0;
        for (int i = 0; i < half; ++i)
            if (num[i] == '?')
                ++blanks;
            else
                difference += num[i] - '0';
        for (int i = half; i != num.size(); ++i)
            if (num[i] == '?')
                --blanks;
            else
                difference -= num[i] - '0';
        if (!blanks)
            return difference;
        if (blanks < 0) {
            blanks = -blanks;
            difference = -difference;
        }
        return ((blanks + 1) >> 1) * 9 + difference > 0 || (blanks >> 1) * 9 + difference < 0;
    }
};