The candidate's solution is complete and solves the problem. The candidate's approach is to use a stack to keep track of the parentheses. Every time the candidate encounters an open parenthesis, they push it onto the stack. Every time the candidate encounters a close parenthesis, they pop off the top element of the stack. If the stack is ever empty when they encounter a close parenthesis, then they know that the string is not balanced. If the stack is not empty when they reach the end of the string, then they know that the string is not balanced.