0682-baseball-game.js

// 682. Baseball Game
// Easy 58% locked:false


// 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.

// Example 1:

// 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.

// Example 2:

// 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.


/**
 * @param {string[]} ops
 * @return {number}
 */
const calPoints = function(ops) {
  const round = ops.length
  let len = -1
  for (let i = 0; i < round; i++) {
    const num = parseInt(ops[i])
    if (num === num) ops[++len] = num
    if (ops[i] === '+') ops[++len] = (ops[len - 1] || 0) + (ops[len - 2] || 0)
    if (ops[i] === 'D') ops[++len] = (ops[len - 1] || 0) * 2
    if (ops[i] === 'C') len--
  }

  let result = 0
  for (let i = 0; i <= len; i++) {
    result += ops[i]
  }

  return result
}

console.log(calPoints(['5','2','C','D','+']))
console.log(calPoints(['5','-2','4','C','D','9','+','+']))
console.log(calPoints(['1','D','D','D']))

// Solution:
// 关键在于读懂问题

// 迭代的时候，记录最后一个有效的轮次的得分，因为迭代过程会执行删去无效轮次的操作（"C")。
// 将数字字符转换成数字。
// "D" 和 "+" 也转换为有效得分，并插在最后一个有效得分的后面。
// 最后将每轮有效得分相加

// Submission Result: Accepted