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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;

}
}