020 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.

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这个就是括号匹配，用数据结构中的栈就可以解决

public class Solution {
    public boolean isValid(String s) {
		LinkedList<Character> linkedList=new LinkedList<>();
		for(int i=0;i<s.length();i++){
			if(s.charAt(i)!='('&&s.charAt(i)!='['&&s.charAt(i)!='{'){
				if(linkedList.isEmpty()){
					return false;
				}else{
					switch(linkedList.pop()){
					case '(':
						if(s.charAt(i)!=')')return false;break;
					case '[':
						if(s.charAt(i)!=']')return false;break;
					case '{':
						if(s.charAt(i)!='}')return false;break;
						
					}
				}
			}else{
				linkedList.push(s.charAt(i));
			}
			
		}
		if(linkedList.isEmpty())return true;
		else return false;
	}
}