Valid Parentheses

Problem Statement

Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.

An input string is valid if:

Open brackets must be closed by the same type of brackets. Open brackets must be closed in the correct order. Every close bracket has a corresponding open bracket of the same type.

Code

Java Code

class Solution {
    public boolean isValid(String s) {
        char [] arr = s.toCharArray();
    Stack stack = new Stack();
    for(char ch : arr){
        if(stack.isEmpty()){
            stack.push(ch);
        }else{
            char top = (char)stack.lastElement();
            if(ch - top == 1 || ch - top == 2){
                stack.pop();
            }else{
                stack.push(ch);
            }
        }
    }
    if(stack.isEmpty()){
        return true;
    }
    return false;

    }
}