# LeetCode.682.Baseball Game

## 题目描述

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.

## 解题过程

package _682_BaseballGame;

import java.util.Stack;

class Solution {
public int calPoints(String[] ops) {
int sum=0;
Stack<Integer> stack = new Stack<Integer>();
for(String op:ops){
try {
Integer score = Integer.valueOf(op);
sum += score;
stack.push(score);//valid分数入栈
} catch (NumberFormatException e) {
if("+".equals(op)){
int lastValid = stack.pop();//先将栈顶弹出
int lastSecondValid = stack.peek();//取栈顶倒数第二个
sum += lastValid + lastSecondValid;
stack.push(lastValid);//再将栈顶push进去
stack.push(lastValid+lastSecondValid);//valid分数入栈
}else if("D".equals(op)){
sum += stack.peek() * 2;
stack.push(stack.peek()*2);//valid分数入栈
}else if("C".equals(op)){
sum -= stack.pop();//弹出栈顶，同时扣分
}
}
System.out.println("sum: "+sum);
}
return sum;
}
}

public class BaseballGame {
public static void main(String[] args){
Solution solution = new Solution();
String[] input1 = {"5","2","C","D","+"};
String[] input2 = {"5","-2","4","C","D","9","+","+"};
System.out.println(solution.calPoints(input1));
}
}

## GitHub代码

813

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