每日一道LeetCode——有效的括号

题目：

解法：利用栈（stack）和哈希Map

import java.util.*;


public class Solution10 {
    public boolean isValid(String s) {
        int n = s.length();
        if (n % 2 == 1) {
            return false;
        }

        Map<Character, Character> pairs = new HashMap<Character, Character>() {{
            put(')', '(');
            put(']', '[');
            put('}', '{');
        }};
        Stack<Character> stack = new Stack<Character>();
        for (int i = 0; i < n; i++) {
            char ch = s.charAt(i);
            if (pairs.containsKey(ch)) {
                if (stack.isEmpty() || stack.peek() != pairs.get(ch)) {
                    return false;
                }
                stack.pop();
            } else {
                stack.push(ch);
            }
        }
        return stack.isEmpty();
    }

    public static void main(String[] args){
        Solution10 s = new Solution10();
        System.out.println(s.isValid("{[()]}"));
    }
}