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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 but "(]" and "([)]" are not.

 1 public class Solution { 2     public boolean isValid(String s) { 3         Stack stack=new Stack(); 4         for(int i=0;i<s.length();i++) 5         { 6             char ch=s.charAt(i); 7             if(ch==‘(‘||ch==‘[‘||ch==‘{‘) 8             { 9                 stack.push(ch);10             }11             else12             {13                 if(!stack.isEmpty())14                 {15                     if(isEqual((char)stack.peek(),ch))16                     {17                         stack.pop();18                     }19                     else20                         return false;21                 }22                 else23                     return false;24             }25         }26         return stack.isEmpty()?true:false;27     }28         public  boolean isEqual(char c1,char c2)29     {30         if(c1==‘[‘&&c2==‘]‘)return true;31         else if(c1==‘(‘&&c2==‘)‘)return true;32         else if(c1==‘{‘&&c2==‘}‘)return true;33         return false;34     }35 }

 

Valid Parentheses