README.md

856. Score of Parentheses

Given a balanced parentheses string s, return the score of the string.

The score of a balanced parentheses string is based on the following rule:

• "()" has score 1.
• AB has score A + B, where A and B are balanced parentheses strings.
• (A) has score 2 * A, where A is a balanced parentheses string.

Example 1:

Input: s = "()"
Output: 1

Example 2:

Input: s = "(())"
Output: 2

Example 3:

Input: s = "()()"
Output: 2

Constraints:

• 2 <= s.length <= 50
• s consists of only '(' and ')'.
• s is a balanced parentheses string.

Solutions (Rust)

1. Solution

impl Solution {
    pub fn score_of_parentheses(s: String) -> i32 {
        let mut stack = vec![];

        for c in s.chars() {
            if c == '(' {
                stack.push(0);
            } else {
                match stack.pop().unwrap() {
                    0 => stack.push(1),
                    x => *stack.last_mut().unwrap() = 2 * x,
                }

                if stack.len() > 1 && stack[stack.len() - 2] > 0 {
                    let x = stack.pop().unwrap();
                    *stack.last_mut().unwrap() += x;
                }
            }
        }

        stack[0]
    }
}