29_Valid Parentheses

/*
Remember while solving:
1)Convey your thoughts clearly to the interviewer
2)Maintain topmost code quality
3)Discuss testcases while solving
4)Evolve from brute->Better->optimal
*/

//Use a stack

//link to the problem:https://leetcode.com/problems/valid-parentheses/
//DSA sheet by Arsh Goyal: Problem 29


class Solution {
    public boolean isValid(String s) {
      int length=s.length();
        Stack<Character> st=new Stack<Character>();
        for(int i=0;i<length;i++){
            char bracket=s.charAt(i);
            if(bracket=='(' || bracket=='{' || bracket=='['){
                st.push(bracket);
            }
            else{
                if(st.empty())
                    return false;
                else{
                    char ch=st.peek();
                    st.pop();
                    if((bracket==')' && ch!='(') || (bracket=='}' && ch!='{') || (bracket==']' && ch!='['))
                        return false;
                }
            }
        }
        if(st.empty())
            return true;
        else
            return false;
    }
}