题解 | #24点游戏算法#

使用枚举法，全排列所有可能顺序，运算符只有64种可能，判断最后结果是否为24即可。注意需要保证除法时要整除得到24才行

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

double cal(int num1, int num2, char opt) {
    if (opt == '+') return num1 + num2;
    else if (opt == '-') return num1 - num2;
    else if (opt == '*') return num1 * num2;
    else return (double)num1 / (double)num2;
}

bool judge(vector<int> nums, char opt[]) {

    sort(nums.begin(), nums.end());

    do {
        for (int i = 0; i < 4; i ++) {
            double num_12 = cal(nums[0], nums[1], opt[i]);
            for (int j = 0; j < 4; j ++) {
                double num_23 = cal(num_12, nums[2], opt[j]);
                for (int k = 0; k < 4; k ++) {
                    double num_34 = cal(num_23, nums[3], opt[k]);
                    if (num_34 == 24.0 ) {
                        // cout << "true" << endl;
                        // cout << num_34 << endl;
                        // cout << nums[0] << opt[i] << nums[1] << opt[j] << nums[2] << opt[k] << nums[3]<< endl;
                        return true;
                    }
                }
            }
        }
    } while (next_permutation(nums.begin(), nums.end()));

    return false;

}
int main() {
    vector<int> nums;
    for (int i = 0 ; i < 4; i ++) {
        int num = 0;
        cin >> num;
        nums.push_back(num);
    }

    char opt[4] = {'+', '-', '*', '/'};

    if(judge(nums, opt))
        cout << "true" << endl;
    else
        cout << "false" << endl;

}
// 64 位输出请用 printf("%lld")