problem

Given a valid parentheses string s, return the nesting depth of s. The nesting depth is the maximum number of nested parentheses.

 

Example 1:

Input: s = "(1+(2*3)+((8)/4))+1"

Output: 3

Explanation:

Digit 8 is inside of 3 nested parentheses in the string.

Example 2:

Input: s = "(1)+((2))+(((3)))"

Output: 3

Explanation:

Digit 3 is inside of 3 nested parentheses in the string.

Example 3:

Input: s = "()(())((()()))"

Output: 3

 

Constraints:

  • 1 <= s.length <= 100
  • s consists of digits 0-9 and characters '+', '-', '*', '/', '(', and ')'.
  • It is guaranteed that parentheses expression s is a VPS.

submission

// simple and straight forward
impl Solution {
    pub fn max_depth(s: String) -> i32 {
        s.chars()
            .scan(0, |depth, ch| {
                match ch {
                    '(' => *depth += 1,
                    ')' => *depth -= 1,
                    _ => {}
                }
                Some(*depth)
            })
            .max()
            .unwrap_or_default()
    }
}