Valid Parentheses
As a Systems Engineer at Tata Consultancy Services, I deliver exceptional software products for mobile and web platforms, using agile methodologies and robust quality maintenance. I am experienced in performance testing, automation testing, API testing, and manual testing, with various tools and technologies such as Jmeter, Azure LoadTest, Selenium, Java, OOPS, Maven, TestNG, and Postman.
I have successfully developed and executed detailed test plans, test cases, and scripts for Android and web applications, ensuring high-quality standards and user satisfaction. I have also demonstrated my proficiency in manual REST API testing with Postman, as well as in end-to-end performance and automation testing using Jmeter and selenium with Java, TestNG and Maven. Additionally, I have utilized Azure DevOps for bug tracking and issue management.
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.
LeetCode Problem - 20
class Solution {
public boolean isValid(String s) {
// Create a stack to store opening parentheses
Stack<Character> str = new Stack<>();
// Iterate through each character in the string
for (int i = 0; i < s.length(); i++) {
char currentChar = s.charAt(i);
// Check if the current character is an opening parenthesis
if (isOpening(currentChar)) {
// Push opening parenthesis onto the stack
str.push(currentChar);
} else {
// If stack is empty, return false as there is no matching opening parenthesis
if (str.isEmpty()) return false;
// If the current closing parenthesis does not match the top opening parenthesis, return false
else if (!isMatching(str.peek(), currentChar)) {
return false;
}
// If the current closing parenthesis matches the top opening parenthesis, pop it from the stack
else str.pop();
}
}
// If stack is empty, all opening parentheses have been matched, return true
return str.isEmpty();
}
// Method to check if a character is an opening parenthesis
boolean isOpening(char c) {
return c == '(' || c == '{' || c == '[';
}
// Method to check if two characters form a valid pair of parentheses
boolean isMatching(char a, char b) {
return (a == '(' && b == ')') || (a == '{' && b == '}') || (a == '[' && b == ']');
}
}
