题解 | #有效括号序列#

import java.util.*;


public class Solution {
    /**
     * 
     * @param s string字符串 
     * @return bool布尔型
     */
    public boolean isValid (String s) {
        // write code here
        Stack<Character> stack = new Stack<>();
        String data = s;
        if(data == null){
            return false;
        }
        for(int i=0;i<data.length();i++){
            if(isLeft(data.charAt(i))){
                stack.push(data.charAt(i));
            }else if(isRight(data.charAt(i))){
                if(stack.isEmpty()){
                        return false;
                    }
                if(needPop(stack.peek(),data.charAt(i))){
                    stack.pop();
                }
            }
        }
        if(stack.isEmpty()){
            return true;
        }else{
            return false;
        }
    }

    private static boolean needPop(Character peek, char charAt) {
        boolean result = false;
        switch(charAt){
            case ')':
                if(peek == '('){
                    result = true;
                }
                break;
            case ']':
                if(peek == '['){
                    result = true;
                }
                break;
            default:
                if(peek == '{'){
                    result = true;
                }
        }
        return result;
    }

    private static boolean isRight(char charAt) {
        if(charAt==']' || charAt == '}' || charAt == ')'){
            return true;
        }else{
            return false;
        }
    }

    private static boolean isLeft(char charAt) {
        if(charAt=='[' || charAt == '{' || charAt == '('){
            return true;
        }else{
            return false;
        }
    }
}