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//! Baseball Game [leetcode: baseball_game](https://leetcode.com/problems/baseball-game/)
//!
//! You're now a baseball game point recorder.
//!
//! Given a list of strings, each string can be one of the 4 following types:
//!
//! 1. `Integer` (one round's score): Directly represents the number of points you get in this round.
//! 2. `"+"` (one round's score): Represents that the points you get in this round are the sum of the last two `valid` round's points.
//! 3. `"D"` (one round's score): Represents that the points you get in this round are the doubled data of the last `valid` round's points.
//! 4. `"C"` (an operation, which isn't a round's score): Represents the last `valid` round's points you get were invalid and should be removed.
//!
//! Each round's operation is permanent and could have an impact on the round before and the round after.
//!
//! You need to return the sum of the points you could get in all the rounds.
//!
//! **Example1:**
//!
//! ```
//! Input: ["5","2","C","D","+"]
//! Output: 30
//! Explanation:
//! Round 1: You could get 5 points. The sum is: 5.
//! Round 2: You could get 2 points. The sum is: 7.
//! Operation 1: The round 2's data was invalid. The sum is: 5.
//! Round 3: You could get 10 points (the round 2's data has been removed). The sum is: 15.
//! Round 4: You could get 5 + 10 = 15 points. The sum is: 30.
//! ```
//!
//! **Example2:**
//!
//! ```
//! Input: ["5","-2","4","C","D","9","+","+"]
//! Output: 27
//! Explanation:
//! Round 1: You could get 5 points. The sum is: 5.
//! Round 2: You could get -2 points. The sum is: 3.
//! Round 3: You could get 4 points. The sum is: 7.
//! Operation 1: The round 3's data is invalid. The sum is: 3.
//! Round 4: You could get -4 points (the round 3's data has been removed). The sum is: -1.
//! Round 5: You could get 9 points. The sum is: 8.
//! Round 6: You could get -4 + 9 = 5 points. The sum is 13.
//! Round 7: You could get 9 + 5 = 14 points. The sum is 27.
//! ```
//!
//! **Note**
//!
//! * The size of the input list will be between 1 and 1000.
//! * Every integer represented in the list will be between -30000 and 30000.
//!
/// # Solutions
///
/// # Approach 1: Stack
///
/// * Time complexity: O(n)
///
/// * Space complexity: O(n)
///
/// * Runtime: 0ms
///
/// Memory: 2.6MB
///
/// ```rust
/// impl Solution {
///     pub fn cal_points(ops: Vec<String>) -> i32 {
///         let mut stack: Vec<i32> = vec![];
///         let mut sum = 0;
///
///         for p in ops.into_iter() {
///             match p.as_ref() {
///                 "+" => {
///                     let top = stack.pop().unwrap();
///                     let new_top = top + stack.last().unwrap();
///                     stack.push(top);
///                     stack.push(new_top);
///                 },
///                 "C" => { stack.pop(); },
///                 "D" => { stack.push(2 * stack.last().unwrap()); },
///                 _ => { stack.push(p.parse::<i32>().unwrap()); },
///             }
///         }
///
///         for score in stack { sum += score; }
///
///         sum
///     }
/// }
/// ```
///
///
/// # Approach 2: Stack
///
/// * Time complexity: O(n)
///
/// * Space complexity: O(1)
///
/// * Runtime: 0ms
///
/// Memory: 2.3MB
///
/// ```rust
/// impl Solution {
///     pub fn cal_points(ops: Vec<String>) -> i32 {
///         let mut stack: Vec<i32> = vec![];
///         let mut sum = 0;
///
///         for p in ops.into_iter() {
///             let mut score = 0;
///             match p.as_ref() {
///                 "+" => { score = stack[stack.len()-1] + stack[stack.len()-2]; },
///                 "C" => {
///                     sum -= stack.pop().unwrap();
///                     continue;
///                 },
///                 "D" => { score = 2 * stack.last().unwrap(); },
///                 _ => { score = p.parse::<i32>().unwrap(); },
///             }
///             sum += score;
///             stack.push(score);
///         }
///         sum
///     }
/// }
/// ```
///
pub fn cal_points(ops: Vec<String>) -> i32 {
    let mut stack: Vec<i32> = vec![];
    let mut sum = 0;

    for p in ops.into_iter() {
        match p.as_ref() {
            "+" => {
                let top = stack.pop().unwrap();
                let new_top = top + stack.last().unwrap();
                stack.push(top);
                stack.push(new_top);
            },
            "C" => { stack.pop(); },
            "D" => { stack.push(2 * stack.last().unwrap()); },
            _ => { stack.push(p.parse::<i32>().unwrap()); },
        }
    }

    for score in stack { sum += score; }

    sum
}