Leetcode-valid parentheses

Given a string containing just the characters‘(‘,‘)‘,‘{‘,‘}‘,‘[‘And‘]‘, Determine if the input string is valid.

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

Solution:

1. If the left parenthesis appears, a matching right parenthesis must be followed.

2. If there is no left parenthesis, there must be no right parenthesis

For 1, open a stack to solve

For example, if there is a right brace, the left brace must already exist (the matching right brace is at the top of the stack)

Open a hashset to judge the right parenthesis.

 1     public boolean isValid(String s) { 2         if(s== null || s.length() ==0){ 3             return true; 4         } 5         Stack<Byte> brackets = new Stack<Byte>(); 6         HashSet<Byte> sets = new HashSet<Byte>(); 7         sets.add((byte) ‘)‘); 8         sets.add((byte) ‘]‘); 9         sets.add((byte) ‘}‘);10         byte [] sBytes = s.getBytes();11         for(int i =0;i<sBytes.length;i++){12             if(sBytes[i] == ‘(‘){13                 brackets.push((byte) ‘)‘);14                 continue;15             }16             if(sBytes[i] == ‘{‘){17                 brackets.push((byte) ‘}‘);18                 continue;19             }20             if(sBytes[i] == ‘[‘){21                 brackets.push((byte) ‘]‘);22                 continue;23             }24             if(sets.contains(sBytes[i])){25                 if(!brackets.isEmpty() && brackets.peek() == sBytes[i]){26                     brackets.pop();27                 }else{28                     return false;29                 }30             }31         }        32         return brackets.isEmpty();33     }

 

Leetcode-valid parentheses