Problem Description
Given a valid parentheses string s (along with digits and operators), return the nesting depth of s. The nesting depth is defined as the maximum number of nested parentheses within the expression.
Key Insights
- Use a counter to track the current nesting level.
- Increment the counter when encountering an opening parenthesis '('.
- Update the maximum depth if the current counter exceeds the previous maximum.
- Decrement the counter when encountering a closing parenthesis ')'.
- Since the input is guaranteed to be a valid parentheses string, no additional checks are required.
Space and Time Complexity
Time Complexity: O(n), where n is the length of the string. Space Complexity: O(1)
Solution
The approach involves iterating over every character in the string once. We maintain two variables: one to count the current level of nesting (currentDepth) and one to store the maximum depth encountered (maxDepth). For every character:
- If it is an opening parenthesis '(', increment currentDepth. Then check and update maxDepth if currentDepth is greater.
- If it is a closing parenthesis ')', decrement currentDepth. This simple counter approach ensures that we determine the maximum nesting depth efficiently using constant extra space.