【LeetCode OJ】Valid Parentheses

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.

java code : 典型栈的应用

public class Solution {    public boolean isValid(String s) {        // Note: The Solution object is instantiated only once and is reused by each test case.        if((s.length() & 1) == 1)return false;    Stack<Character> st = new Stack<Character>();for(int i = 0; i < s.length(); i++){if(i == 0 || isLeft(s.charAt(i)))st.add(s.charAt(i));else{if(st.isEmpty())return false;if(isMatch(st.peek(), s.charAt(i)))st.pop();else return false;}}return st.isEmpty();    }    public boolean isLeft(char ch){if(ch == '(' || ch == '[' || ch == '{')return true;return false;}public boolean isMatch(char x, char y){if((x == '(' && y == ')') || (x == '[' && y == ']') || (x == '{' && y == '}'))return true;return false;}}