华为机试：24点运算

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

int cacul(int a, int b, char op) {
    switch(op) {
        case '+': return a + b;
        case '-': return a - b;
        case '*': return a * b;
        case '/': return a / b;
    }
    return 0;
}

int main() {
    vector<string> p = {"0", "A", "2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K"};
    string poker;
    getline(cin, poker);
    vector<int> nums;
    for (char ch : poker) {
        if (ch >= '2' && ch <= '9') nums.push_back(ch - '0');
        if (ch == '1') nums.push_back(10);
        if (ch == 'J') nums.push_back(11);
        if (ch == 'Q') nums.push_back(12);
        if (ch == 'K') nums.push_back(13);
        if (ch == 'A') nums.push_back(1);
        if (ch == 'o' || ch == 'O') {
            cout << "ERROR" << endl;
            return 0;
        }
    }
    string op = "+-*/";
    sort(nums.begin(), nums.end());
    do {
        for (char op1 : op) {
            for (char op2 : op) {
                for (char op3 : op) {
                    int first = cacul(nums[0], nums[1], op1);
                    int second = cacul(first, nums[2], op2);
                    int third = cacul(second, nums[3], op3);
                    if (third == 24) {
                        cout << p[nums[0]] << op1 << p[nums[1]] << op2 << p[nums[2]] << op3 << p[nums[3]];
                        return 0;
                    }
                }
            }
        }
    }while (next_permutation(nums.begin(), nums.end()));
    cout << "NONE" << endl;
    return 0;
}