java-NC52_有效括号序列

java-NC52 有效括号序列

import java.util.*;

/**
 * NC52 有效括号序列
 * @author d3y1
 */
public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param s string字符串
     * @return bool布尔型
     */
    public boolean isValid (String s) {
        // 栈
        Stack<Character> stack = new Stack<>();
        for(char ch: s.toCharArray()){
            switch(ch){
                case '(':
                case '[':
                case '{':
                    stack.push(ch);
                    break;
                case ')':
                    if(stack.isEmpty() || stack.peek()!='('){
                        return false;
                    }
                    stack.pop();
                    break;
                case ']':
                    if(stack.isEmpty() || stack.peek()!='['){
                        return false;
                    }
                    stack.pop();
                    break;
                case '}':
                    if(stack.isEmpty() || stack.peek()!='{'){
                        return false;
                    }
                    stack.pop();
                    break;
            }
        }

        return stack.isEmpty();
    }
}