Someone suggests that you might not need a stack to match parentheses in expressions after all. Instead, you can set a counter to 0, increment it when a left parenthesis is encountered, and decrement it whenever a right parenthesis is seen. If the counter ever goes below zero or remains positive at the end of the process, there was an error; if the counter is zero at the end and never goes negative, the parentheses all match correctly. Where does this strategy break down? (Hint: There might be braces and brackets to match as well.)
