[후위 표기식2 - 백준] / Stack, queue

Problem

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https://www.acmicpc.net/problem/1935

1935번: 후위 표기식2

Solve

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#include <iostream>
#include <stack>
#include <queue>

using namespace std;

class sol
{
	int N;
	string str;
	int number[30];
	double answer;

	stack<double> q;
	queue<char> s;

public:
	sol(const int& cnt, const string& s)
	{
		N = cnt;
		str = s;
	}

	void input_data()
	{
		int n;
		for (int i = 0; i < N; i++)
		{
			cin >> n;
			number[i] = n;
		}
	}

	void solution()
	{
		for (int i = 0; i < str.length();)
		{
			while (str[i]>='A' && str[i] <='Z')
			{
				//char cha = str[i++];
				int index = str[i++] - 'A';
				q.push(number[index]);
			}

			while (str[i]<'A' || str[i] > 'Z')
			{
				s.push(str[i++]);
				if (i==str.length())
				{
					break;
				}
			}

			double first;
			double second;
			double result = q.top();
			q.pop();
			while (!s.empty())
			{
				first = result;
				//q.pop();
				second = q.top();
				q.pop();

				char c = s.front();
				s.pop();
				switch (c)
				{
				case '*':
					result = second * first; break;
				case '/':
					result = second / first; break;
				case '+':
					result = second + first; break;
				case '-':
					result = second - first; break;
				default:
					break;
				}
			}
			q.push(result);
			//answer = result;
		}
        
		cout << fixed;					// 출력 시 소수점 자리 표기
		cout.precision(2);
        
		cout << q.top();
	}
};

int main()
{
	int N;
	cin >> N;
	string str;
	cin >> str;

	sol S(N, str);

	S.input_data();
	S.solution();
	return 0;
}