Leetcode题解 495.Teemo Attacking 【Array】

In LOL world, there is a hero called Teemo and his attacking can make his enemy Ashe be in poisoned condition. Now, given the Teemo's attacking ascending time series towards Ashe and the poisoning time duration per Teemo's attacking, you need to output the total time that Ashe is in poisoned condition.

You may assume that Teemo attacks at the very beginning of a specific time point, and makes Ashe be in poisoned condition immediately.

Example 1:

Input: [1,4], 2
Output: 4
Explanation: At time point 1, Teemo starts attacking Ashe and makes Ashe be poisoned immediately. 
This poisoned status will last 2 seconds until the end of time point 2.
And at time point 4, Teemo attacks Ashe again, and causes Ashe to be in poisoned status for another 2 seconds.
So you finally need to output 4.

Example 2:

Input: [1,2], 2
Output: 3
Explanation: At time point 1, Teemo starts attacking Ashe and makes Ashe be poisoned. 
This poisoned status will last 2 seconds until the end of time point 2.
However, at the beginning of time point 2, Teemo attacks Ashe again who is already in poisoned status.
Since the poisoned status won't add up together, though the second poisoning attack will still work at time point 2, it will stop at the end of time point 3.
So you finally need to output 3.

Note:

1. You may assume the length of given time series array won't exceed 10000.
2. You may assume the numbers in the Teemo's attacking time series and his poisoning time duration per attacking are non-negative integers, which won't exceed 10,000,000.

Solution: It probably means that Teemo will blind Ashe. Given a list and an integer, the elements in the list (in ascending order) represent the time when Teemo blinded Ashe, and the integer represents the duration of Teemo's blinding effect. Suppose Ashe is blinded immediately after Teemo attacks.

Idea: Establish two variables, total, now, total represents the total blinding time, now represents the first second of Ashe's vision recovery after being blinded, initialized to -1 (because the time axis starts from 0, it can be considered that at the beginning of Ashe Hope has normal vision. So now is set to -1)

Next, time points are sequentially extracted from the list and set as i.

There are two cases, one is i > now, which means that Ashe had normal vision when Teemo attacked Ashe. In this case, you only need to directly calculate total+=duration, because the blinding time does not overlap.

The second is i > now - duration + 1

This situation indicates that Ashe has been blinded when Teemo attacks Ashe, and the remaining blinding time will be refreshed at this time, so total += duration -(now-i+1)

now-i+1 represents the effective time of the previous blinding, duration - (now-i+1) represents the effective time of the second blinding.

Note that now should be updated accordingly after each calculation of total

Ac code is as follows:

class Solution:
    def findPoisonedDuration(self, timeSeries, duration):
        """
        :type timeSeries: List[int]
        :type duration: int
        :rtype: int
        """
        total = 0
        now = -1
        for i in timeSeries:
            if i > now:
                total += duration
                now = i + duration - 1
            elif i > now - duration + 1:
                total += duration - (now - i + 1)
                now += duration - (now - i + 1)
        return total