[Leetcode]-valid parentheses (valid brackets)

[Problem:]

Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.
Literal Translation: a string containing the characters '(', ')', '{', '}', '[', ']'. Check whether the string is valid.

The brackets must close in the correct order, "()" and "() [] {}" are all valid but "(]" and "([)]" are not.

[Solution:]

Solution: Use the stack data structure. If the character entered cannot match left or right, press the stack. If it can match, the stack is played and the next loop starts.

When the loop ends, if the stack is still empty, the brackets are valid.

import java.util.HashMap;import java.util.Map;import java.util.Stack;public class Solution {public static void main(String[] args) {System.out.println(new Solution().isValid("{[()]}"));}public boolean isValid(String s) {if (s != null && !"".equals(s.trim())) {// init the character mapMap<Character, Character> map = init();Stack<Character> stack = new Stack<Character>();char[] ch = s.toCharArray();for (int i = 0; i < ch.length; i++) {// the first time come into the loopif (stack.size() == 0) {stack.push(ch[i]);} else {Character pre = stack.peek(); if (pre.equals(map.get(ch[i]))) {stack.pop();continue;}stack.push(ch[i]);}}// the stack is emptyif (stack.size() == 0) {return true;}}return false;}/** * data init. * @return Map<Character> */public Map<Character, Character> init() {Map<Character, Character> map = new HashMap<Character, Character>();map.put('(', ')');map.put(')', '(');map.put('{', '}');map.put('}', '{');map.put('[', ']');map.put(']', '[');return map;}}

[Leetcode]-valid parentheses (valid brackets)