Question

682. Baseball Game

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Description

You are keeping the scores for a baseball game with strange rules. At the beginning of the game, you start with an empty record.

You are given a list of strings operations, where operations[i] is the ith operation you must apply to the record and is one of the following:

• An integer x.
  • Record a new score of x.
• '+'.
  • Record a new score that is the sum of the previous two scores.
• 'D'.
  • Record a new score that is the double of the previous score.
• 'C'.
  • Invalidate the previous score, removing it from the record.

Return _the sum of all the scores on the record after applying all the operations_.

The test cases are generated such that the answer and all intermediate calculations fit in a 32-bit integer and that all operations are valid.

 

Example 1:

Input: ops = ["5","2","C","D","+"]
Output: 30
Explanation:
"5" - Add 5 to the record, record is now [5].
"2" - Add 2 to the record, record is now [5, 2].
"C" - Invalidate and remove the previous score, record is now [5].
"D" - Add 2 * 5 = 10 to the record, record is now [5, 10].
"+" - Add 5 + 10 = 15 to the record, record is now [5, 10, 15].
The total sum is 5 + 10 + 15 = 30.

Example 2:

Input: ops = ["5","-2","4","C","D","9","+","+"]
Output: 27
Explanation:
"5" - Add 5 to the record, record is now [5].
"-2" - Add -2 to the record, record is now [5, -2].
"4" - Add 4 to the record, record is now [5, -2, 4].
"C" - Invalidate and remove the previous score, record is now [5, -2].
"D" - Add 2 * -2 = -4 to the record, record is now [5, -2, -4].
"9" - Add 9 to the record, record is now [5, -2, -4, 9].
"+" - Add -4 + 9 = 5 to the record, record is now [5, -2, -4, 9, 5].
"+" - Add 9 + 5 = 14 to the record, record is now [5, -2, -4, 9, 5, 14].
The total sum is 5 + -2 + -4 + 9 + 5 + 14 = 27.

Example 3:

Input: ops = ["1","C"]
Output: 0
Explanation:
"1" - Add 1 to the record, record is now [1].
"C" - Invalidate and remove the previous score, record is now [].
Since the record is empty, the total sum is 0.

 

Constraints:

• 1 <= operations.length <= 1000
• operations[i] is "C", "D", "+", or a string representing an integer in the range [-3 * 104, 3 * 104].
• For operation "+", there will always be at least two previous scores on the record.
• For operations "C" and "D", there will always be at least one previous score on the record.

Solutions

Solution 1

class Solution:
  def calPoints(self, ops: List[str]) -> int:
    stk = []
    for op in ops:
      if op == '+':
        stk.append(stk[-1] + stk[-2])
      elif op == 'D':
        stk.append(stk[-1] << 1)
      elif op == 'C':
        stk.pop()
      else:
        stk.append(int(op))
    return sum(stk)

class Solution {
  public int calPoints(String[] ops) {
    Deque<Integer> stk = new ArrayDeque<>();
    for (String op : ops) {
      if ("+".equals(op)) {
        int a = stk.pop();
        int b = stk.peek();
        stk.push(a);
        stk.push(a + b);
      } else if ("D".equals(op)) {
        stk.push(stk.peek() << 1);
      } else if ("C".equals(op)) {
        stk.pop();
      } else {
        stk.push(Integer.valueOf(op));
      }
    }
    return stk.stream().mapToInt(Integer::intValue).sum();
  }
}

class Solution {
public:
  int calPoints(vector<string>& ops) {
    vector<int> stk;
    for (auto& op : ops) {
      int n = stk.size();
      if (op == "+") {
        int a = stk[n - 1];
        int b = stk[n - 2];
        stk.push_back(a + b);
      } else if (op == "D")
        stk.push_back(stk[n - 1] * 2);
      else if (op == "C")
        stk.pop_back();
      else
        stk.push_back(stoi(op));
    }
    return accumulate(stk.begin(), stk.end(), 0);
  }
};

func calPoints(ops []string) int {
  var stk []int
  for _, op := range ops {
    n := len(stk)
    switch op {
    case "+":
      stk = append(stk, stk[n-1]+stk[n-2])
    case "D":
      stk = append(stk, stk[n-1]*2)
    case "C":
      stk = stk[:n-1]
    default:
      num, _ := strconv.Atoi(op)
      stk = append(stk, num)
    }
  }
  ans := 0
  for _, score := range stk {
    ans += score
  }
  return ans
}

function calPoints(ops: string[]): number {
  const stack = [];
  for (const op of ops) {
    const n = stack.length;
    if (op === '+') {
      stack.push(stack[n - 1] + stack[n - 2]);
    } else if (op === 'D') {
      stack.push(stack[n - 1] * 2);
    } else if (op === 'C') {
      stack.pop();
    } else {
      stack.push(Number(op));
    }
  }
  return stack.reduce((p, v) => p + v);
}

impl Solution {
  pub fn cal_points(ops: Vec<String>) -> i32 {
    let mut stack = vec![];
    for op in ops {
      match op.as_str() {
        "+" => {
          let n = stack.len();
          stack.push(stack[n - 1] + stack[n - 2]);
        }
        "D" => {
          stack.push(stack.last().unwrap() * 2);
        }
        "C" => {
          stack.pop();
        }
        n => {
          stack.push(n.parse::<i32>().unwrap());
        }
      }
    }
    stack.into_iter().sum()
  }
}