LeetCode.20_[栈]_有效的括号

1.题目

2.解题思路

检测到左括号，入栈
检测1到右括号，检查栈顶元素，匹配则出栈

3.代码实现

class Solution {
    public boolean isValid(String s) {
        Stack<Character> stack = new Stack<Character>();
        for(int i = 0; i < s.length(); i++){
            char item = s.charAt(i);
            if(item == '(' || item == '[' || item == '{' ){
                stack.push(item);
                continue;
            }
			if(!stack.isEmpty()) {
				if(item == ')' && stack.peek() == '(' ) 
				    stack.pop();
				else if(item == ']' && stack.peek() == '[' ) 
				    stack.pop();
				else if(item == '}' && stack.peek() == '{' ) 
				    stack.pop();
                else
                    return false;
			}else
				stack.push(item);
        }
        if(stack.isEmpty()) return true;
        else return false;
    }
}