Check for balanced parentheses using stack【1月20日学习笔记】

//Check for balanced parentheses using stack
#include<iostream>
#include<stack>//stack from standard template library（STL）
#include<string>
using namespace std;

bool arepair(char opening, char closing) {
	if (opening == '(' && closing == ')')   return true;
	else if (opening == '{' && closing == '}')   return true;
	else if (opening == '[' && closing == ']')   return true;
	return false;
}//判断是否匹配

bool AreParanthesesBalanced(string exp) {
	stack<char> S;
	for (int i = 0; i < exp.length(); i++) {//遍历整个字符串，只关心括号即可
		if (exp[i] == '(' || exp[i] == '{' || exp[i] == '[')//开括号push
			S.push(exp[i]);
		else if (exp[i] == ')' || exp[i] == '}' || exp[i] == ']')//闭括号两种情况
		{
			if (S.empty() || !arepair(S.top(), exp[i]))//stack为空或者与上一括号不匹配
				return false;
			else
				S.pop();//匹配时pop掉上一括号
		}
	}
	return S.empty() ? true : false;//检测最终stack是否为空
}

int main() {
	string expression;
	cin >> expression;
	if (AreParanthesesBalanced(expression))
		cout << "balanced" << endl;
	else cout << "not balanced" << endl;
}