Challenge

Given a string containing just the char '(' , ')' , '[' , ']' , '{' , '}'

Determine if the 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. Note that an empty string is also considered valid.

Example 1: Input : '( )' Output : True

Example 2: Input : '( ) [ ] { }' Output : True

Example 3: Input : '( ]' Output : False

Example 4: Input : '( [ ) ]' Output : False