Kick the ball!

题意：

给出每队的点球得分概率，求得分为a-b的概率

分析：

dfs搜每一种结果

实现：

bool check(int a, int b, int t)
{
    if (a - b - (t + 1) / 2 > 0)
        return true;
    if (b - a - t / 2 > 0)
        return true;
    return false;
}
void dfs(int a, int b, int k, double tmp)
{
    if (k == 10)
    {
        if (resa == a && resb == b)
        {
            res += tmp;
        }
        return;
    }

    if (check(a, b, 10 - k))
    {
        dfs(a, b, k + 1, tmp);
        return;
    }

    if (k & 1)
    {
        dfs(a, b + 1, k + 1, tmp * p[k]);
        dfs(a, b, k + 1, tmp * (1 - p[k]));
    }
    else
    {
        dfs(a + 1, b, k + 1, tmp * p[k]);
        dfs(a, b, k + 1, tmp * (1 - p[k]));
    }
}
void solve()
{
    res = 0;
    scanf("%lld-%lld", &resa, &resb);

    dfs(0, 0, 0, 1.0);

    printf("Case %lld: %.2lf%%\n", idx++, res * 100);
}
signed main()
{
    while (~scanf("%lf %lf %lf %lf %lf %lf %lf %lf %lf %lf", &p[0], &p[2], &p[4], &p[6], &p[8], &p[1], &p[3], &p[5], &p[7], &p[9]))
        solve();
    return 0;
}