题解 | #24点游戏算法#

// 1. 注意数据类型要选择double
// 2. 下一个全排列  next_permutation的使用
#include <algorithm>
#include<iostream>
#include <vector>
using namespace std;

vector<char> op{'+', '-', '*', '/'};
double cal(double a, double b, char ch){
    switch (ch) {
        case '+': return a + b;
        case '-': return a - b;
        case '*': return a * b;
        case '/': return a / b;
    }

    return 0;
}


int main(){
    vector<double> v(4);
    cin >> v[0] >> v[1] >> v[2] >> v[3];
    sort(v.begin(), v.end());

    do{
        for(int i = 0; i < 4; ++i){
            for(int j = 0; j < 4; ++j){
                for(int k = 0; k < 4; ++k){
                    double tmp = 0;
                    tmp = cal(v[0], v[1], op[i]);
                    tmp = cal(tmp, v[2], op[j]);
                    tmp = cal(tmp, v[3], op[k]);
                    if(tmp == 24){
                        cout << "true" << endl;
                        return 0;
                    }
                    
                }
            }
        }

    }while(next_permutation(v.begin(), v.end()));
    cout << "false" << endl;
    return 0;
}