[LeetCode] 127: Valid Parentheses

最新推荐文章于 2021-05-19 14:51:40 发布

原创最新推荐文章于 2021-05-19 14:51:40 发布 · 3.6k 阅读

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本文介绍了一种使用栈数据结构来验证包含括号的字符串是否有效的算法。该算法能正确判断括号是否成对出现并正确闭合，适用于编程面试和技术评估场景。

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[Problem]

Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.

The brackets must close in the correct order, "()" and "()[]{}" are all valid but "(]" and "([)]" are not.

[Solution]

class Solution {
public:
	bool isValid(string s) {
		// Note: The Solution object is instantiated only once and is reused by each test case.
		stack<char> myStack;
		for(int i = 0; i < s.size(); ++i){
			if(s[i] == ']'){
				if(!myStack.empty() && myStack.top() == '['){
					myStack.pop();
				}
				else{
					return false;
				}
			}
			else if(s[i] == ')'){
				if(!myStack.empty() && myStack.top() == '('){
					myStack.pop();
				}
				else{
					return false;
				}
			}
			else if(s[i] == '}'){
				if(!myStack.empty() && myStack.top() == '{'){
					myStack.pop();
				}
				else{
					return false;
				}
			}
			else{
				myStack.push(s[i]);
			}
		}
		return myStack.empty();
	}
};