Question

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.

Answer 1

To determine the validity of a string containing brackets, use a stack to check if the open and close brackets are balanced and in the correct order.

Step-by-step explanation:

Given a string s containing just the characters '(', ')', '{', '}', '[', and ']', we can determine if the input string is valid by using a stack as follows:

1. Create an empty stack.
2. Iterate through each character in the string:
3. If the character is an open bracket, push it onto the stack.
4. If the character is a close bracket, check if the stack is empty or the top element of the stack is not the corresponding open bracket. If either condition is true, the string is invalid. Otherwise, pop the top element of the stack.
5. After iterating through all characters, if the stack is empty, the string is valid. Otherwise, it is invalid.

For example, if the input string is '{[()]}', the algorithm will push '{', '[', and '(' onto the stack, and then pop them in the correct order. At the end, the stack will be empty, indicating a valid string.