求和游戏

// 思路：
// 1. 将字符串的前后两部分分开。
// 2. 使用流处理前后两部分的和，统计问号的数量。
// 3. 使用流判断是否存在使和相等的情况。

import java.util.stream.IntStream;

public class GameSolutionStream {
    public boolean isAliceWinning(String num) {
        int n = num.length();
        int half = n / 2;

        int leftSum = IntStream.range(0, half)
                .filter(i -> num.charAt(i) != '?')
                .map(i -> num.charAt(i) - '0')
                .sum();

        int rightSum = IntStream.range(half, n)
                .filter(i -> num.charAt(i) != '?')
                .map(i -> num.charAt(i) - '0')
                .sum();

        long leftQuestionMarks = IntStream.range(0, half)
                .filter(i -> num.charAt(i) == '?')
                .count();

        long rightQuestionMarks = IntStream.range(half, n)
                .filter(i -> num.charAt(i) == '?')
                .count();

        int diff = leftSum - rightSum;
        int qDiff = (int) ((rightQuestionMarks - leftQuestionMarks) * 9);

        return diff != qDiff;
    }
}