LeetCode20_Valid Parentheses effective brackets

topic:

Includes only a given '(', ')' string, '{', '}', '[', ']', and determine whether the string is valid.

Valid string must meet:

Left bracket must be closed by a closing parenthesis of the same type.
Left parenthesis must be closed in the correct order.
Note the empty string can be considered a valid string.

Source: stay button (LeetCode)
link: https: //leetcode-cn.com/problems/valid-parentheses
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Ideas:

The use of a stack data structure;

 

Java implementation:

 1 import java.util.Stack;
 2 
 3 class Solution {
 4     public boolean isValid(String s) {
 5         
 6         Stack<Character> stack = new Stack<>();
 7         for (int i = 0; i<s.length(); i++){
 8             char c = s.charAt(i);
 9             if(c == '('||c == '['|| c == '{')
10                 stack.push(c);
11             else{
12                 if(stack.isEmpty())
13                     return false;
14                 char topChar = stack.pop();
15                 if(c==')'&& topChar != '(')
16                     return false;
17                 if(c==']'&& topChar != '[')
18                     return false;
19                 if(c=='}'&& topChar != '{')
20                     return false;
21             }
22         }
23         return stack.isEmpty();
24     }
25 }