495. Teemo Attacking

Problem

Our hero Teemo is attacking an enemy Ashe with poison attacks! When Teemo attacks Ashe, Ashe gets poisoned for a exactly duration seconds. More formally, an attack at second t will mean Ashe is poisoned during the inclusive time interval [t, t + duration - 1]. If Teemo attacks again before the poison effect ends, the timer for it is reset, and the poison effect will end duration seconds after the new attack.

You are given a non-decreasing integer array timeSeries, where timeSeries[i] denotes that Teemo attacks Ashe at second timeSeries[i], and an integer duration.

Return **the *total* number of seconds that Ashe is poisoned**.

  Example 1:

Input: timeSeries = [1,4], duration = 2
Output: 4
Explanation: Teemo's attacks on Ashe go as follows:
- At second 1, Teemo attacks, and Ashe is poisoned for seconds 1 and 2.
- At second 4, Teemo attacks, and Ashe is poisoned for seconds 4 and 5.
Ashe is poisoned for seconds 1, 2, 4, and 5, which is 4 seconds in total.

Example 2:

Input: timeSeries = [1,2], duration = 2
Output: 3
Explanation: Teemo's attacks on Ashe go as follows:
- At second 1, Teemo attacks, and Ashe is poisoned for seconds 1 and 2.
- At second 2 however, Teemo attacks again and resets the poison timer. Ashe is poisoned for seconds 2 and 3.
Ashe is poisoned for seconds 1, 2, and 3, which is 3 seconds in total.

  Constraints:

• 1 <= timeSeries.length <= 10^4

• 0 <= timeSeries[i], duration <= 10^7

• timeSeries is sorted in non-decreasing order.

Solution (Java)

class Solution {
    public int findPoisonedDuration(int[] timeSeries, int duration) {
        if (duration == 0) {
            return 0;
        }
        int start = timeSeries[0];
        int end = timeSeries[0] + duration - 1;
        int poisonDuration = end - start + 1;
        for (int i = 1; i < timeSeries.length; i++) {
            if (timeSeries[i] <= end) {
                poisonDuration += (duration - (end - timeSeries[i] + 1));
                end += (duration - (end - timeSeries[i] + 1));
            } else {
                start = timeSeries[i];
                end = timeSeries[i] + duration - 1;
                poisonDuration += end - start + 1;
            }
        }
        return poisonDuration;
    }
}

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).