682. Baseball Game


Baseball Game

Baseball Game 

Problem Description

You are keeping score for a baseball game with strange rules. The game consists of several rounds, where the scores of past rounds may affect future rounds' scores.

At the beginning of the game, you start with an empty record. You are given a list of strings ops, where ops[i] is the ith the operation you must apply to the record is one of the following:

  1. An integer x - Record a new score of x.
  2. "+" - Record a new score that is the sum of the previous two scores. It is guaranteed there will always be two previous scores.
  3. "D" - Record a new score that is double the previous score. It is guaranteed there will always be a previous score.
  4. "C" - Invalidate the previous score, removing it from the record. It is guaranteed there will always be a previous score.

Return the sum of all the scores on the record. The test cases are generated so that the answer fits in a 32-bit integer.

 

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 <= ops.length <= 1000
  • ops[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.

Approach (Using Stack)

/**
 * @param {string[]} ops
 * @return {number}
 */
var calPoints = function(ops) {
    let stack = [];
    let sum = 0;
    for(let i=0;i<ops.length;i++){
        if(ops[i] == 'C'){
            stack.pop(); 
        }else if(ops[i] == '+'){
            stack.push(Number(stack[stack.length-1] || 0) + Number(stack[stack.length-2] || 0)); 
        }else if(ops[i] == 'D'){
            stack.push(stack[stack.length-1] * 2); 
        }else if((!isNaN(ops[i])) && typeof(Number(ops[i])) == 'number'){
            stack.push(ops[i]);
        }
    }
    return  stack.reduce(
              (previousValue, currentValue) => Number(previousValue) + Number(currentValue),
              0
            );
};
Runtime: 70 ms, faster than 87.59% of JavaScript online submissions for Baseball Game.
Memory Usage: 42.6 MB, less than 49.49% of JavaScript online submissions for Baseball Game.

Complexity analysis.

Time Complexity

    We are traversing through the complete array which needs O(N).

Space Complexity

    
We are using a stack as an extra space, hence space complexity is O(N).


Conclusion

That’s all folks! In this post, we solved LeetCode problem #682. Baseball Game 

I hope you have enjoyed this post. Feel free to share your thoughts on this.

You can find the complete source code on my GitHub repository. If you like what you learn. feel free to fork 🔪 and star ⭐ it.


In this blog, I have tried to collect & present the most important points to consider when improving Data structure and logic, feel free to add, edit, comment, or ask. For more information please reach me here
Happy coding!

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