Valid Parentheses - Algorithm

The algorithm is simple:

$1.$ For each character in the string:

• If it's an open bracket, push it onto the stack.
• If it's a close bracket, check if the stack is non-empty and the top matches. If so, pop. Otherwise, return false.

$2.$ After processing all characters, return true if the stack is empty. An empty stack at the end means every open found its matching close. Time: $O(n)$. Space: $O(n)$.