LeetCode & Q20-Valid Parentheses-Easy

Stack String

Description:

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.

堆栈的典型例子

my Solution:

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