Valid Parentheses

Problem

Determine whether the string s made of bracket characters is balanced.

Use a stack: push every opening bracket, and on a closing bracket verify it matches the most recent unmatched opener. Return True for the empty string and False on any mismatch or leftover opener.

Hint

A closing bracket must match the most recently opened one, which is exactly a last-in-first-out check.

Test cases

case 1

in: ["()"]

expected: true

case 2

in: ["()[]{}"]

expected: true

case 3

in: ["(]"]

expected: false

case 4

in: ["([{}])"]

expected: true

case 5

in: [""]

expected: true

Starter codePython

def is_valid_parentheses(s):
    # Your code here
    pass

5 test cases · run your code against them in the editor