【leetcode】第20题 Valid Parentheses 题目+解析+代码

【题目】

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.

【解析】

就是() {} [] 要成对的出现，比如( { [ ] } )等。

【代码】

public class Solution {
	public boolean isValid(String s) {
		char[] stack = new char[s.length()];
		int head = 0;
		char[] cs = s.toCharArray();  
                for(int i=0;i<cs.length;i++){  
			switch(cs[i]) {
				case '{':
				case '[':
				case '(':
					stack[head] = cs[i];   
                                        head++;
					break;
				case '}':
					if(head == 0 || stack[head-1] != '{') return false;
                                        head--;
					break;
				case ')':
					if(head == 0 || stack[head-1] != '(') return false;
                                        head--;
					break;
				case ']':
					if(head == 0 || stack[head-1] != '[') return false;
					head--;
                                        break;
			}
		}
		return head == 0;

	}
}