c＋＋，用扑克牌实现24点游戏

以下是使用C++实现24点纸牌游戏的示例代码：

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

const double eps = 1e-6;
const int N = 4;
double a[N];

bool dfs(vector<double>& nums) {
    if (nums.size() == 1) {
        return fabs(nums[0] - 24) < eps;
    }
    for (int i = 0; i < nums.size(); i++) {
        for (int j = i + 1; j < nums.size(); j++) {
            double x = nums[i], y = nums[j];
            vector<double> next_nums = {x + y, x - y, y - x, x * y};
            if (fabs(y) > eps) {
                next_nums.push_back(x / y);
            }
            if (fabs(x) > eps) {
                next_nums.push_back(y / x);
            }
            nums.erase(nums.begin() + j);
            nums.erase(nums.begin() + i);            for (double next_num : next_nums) {
                nums.push_back(next_num);
                if (dfs(nums)) {
                    return true;
                }
                nums.pop_back();
            }
            nums.insert(nums.begin() + i, x);
            nums.insert(nums.begin() + j, y);
        }
    }
    return false;
}

int main() {
    while (cin >> a[0] >> a[1] >> a[2] >> a[3]) {
        sort(a, a + N);
        bool flag = false;
        do {
            vector<double> nums(a, a + N);
            if (dfs(nums)) {
                flag = true;
                break;
            }
        } while (next_permutation(a, a + N));
        if (flag) {
            cout << "YES" << endl;
        } else {
            cout << "NO" << endl;
        }
    }
    return 0;
}