CCF 201903-2 二十四点

CCF 201903-2 二十四点

//
// Created by asimov on 2020/3/20.
//CCF
//201903-2 二十四点
//
#ifndef CSP_24P_H
#define CSP_24P_H
#endif //CSP_24P_H

#include <bits/stdc++.h>

using namespace std;

stack<int> numStack;//操作数栈
stack<char> operationStack;//操作符栈
string str;

int p() {
    int n, front, back, i, j;
    cin >> n;
    getchar(); //读取换行符,易漏！！！
    for (i = 0; i < n; i++) {
        while (!numStack.empty()) numStack.pop();//清空栈
        while (!operationStack.empty()) operationStack.pop();
        cin >> str;//读取字符串
        //cout<<str.length()<<endl;

        for (j = 0; j < str.length(); j++) {
            if (str[j] >= '0' && str[j] <= '9')//若为数字，压入nd栈中
            {
                numStack.push(str[j] - '0');
            } else if (str[j] == '+') //若为'+',压入op栈中
            {
                operationStack.push('+');
            } else if (str[j] == '-')//转化为"+"计算(即将正数存储为负数,而op栈中就可以存放'+'了)
            {
                numStack.push((str[j + 1] - '0') * (-1));
                operationStack.push('+');
                j++;
            } else if (str[j] == 'x')//先乘除法，与下一个未压入栈的数字计算，将计算结果压入数栈；
            {
                front = numStack.top();
                numStack.pop();
                back = str[j + 1] - '0';
                numStack.push(front * back);
                j++;//已经使用了后一位操作数 因此跳过
            } else if (str[j] == '/') {
                front = numStack.top();
                numStack.pop();
                back = str[j + 1] - '0';
                numStack.push(front / back);
                j++;
            }
        }
        while (!operationStack.empty())//此时只剩下'+'未计算了
        {
//            取两个操作数
            front = numStack.top();
            numStack.pop();
            back = numStack.top();
            numStack.pop();

            operationStack.pop();
            numStack.push(front + back);
        }
        //  cout<<numStack.top()<<endl;
        if (numStack.top() == 24)//取出栈中数字，看是否=24
            cout << "Yes" << endl;
        else
            cout << "No" << endl;
    }
    return 0;
}

/*
10
9+3+4x3
5+4x5x5
7-9-9+8
5x6/5x4
3+5+7+9
1x1+9-9
1x9-5/9
8/5+6x9
6x7-3x6
6x4+4/5
*/