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| 1 | +# [Problem 1701: Average Waiting Time](https://leetcode.com/problems/average-waiting-time/description/?envType=daily-question) |
| 2 | + |
| 3 | +## Initial thoughts (stream-of-consciousness) |
| 4 | +- Given the length of the customer list, I think we'll need to find an $O(n)$ solution |
| 5 | +- Things to track: |
| 6 | + - Total wait time so far |
| 7 | + - Number of customers (this is just `len(customers)`, so we don't actually need to "track" it per se...but still) |
| 8 | + - Current time that the chef is occupied until |
| 9 | +- Any special cases? 🤔... |
| 10 | + - What if all of the arrival times are the same? --> Then the average wait time is just `sum([c[1] for c in customers]) / len(customers)` |
| 11 | + - Arrival times are already sorted, so no need to rearrange the list... |
| 12 | + |
| 13 | +## Refining the problem, round 2 thoughts |
| 14 | +- Let's start with `totalWait = 0` and `chefBusyUntil = 0` |
| 15 | +- With each new customer (`[x, y]`): |
| 16 | + - If `x < chefBusyUntil`: |
| 17 | + - `totalWait += chefBusyUntil - x` # wait until the chef is done with the current workload |
| 18 | + - Else: |
| 19 | + - `chefBusyUntil = x` # need to wait until the next customer arrives to start on their request |
| 20 | + - `totalWait += y` |
| 21 | + - `chefBusyUntil += y` |
| 22 | +- Then return `totalWait / len(customers)` |
| 23 | + |
| 24 | +## Attempted solution(s) |
| 25 | +```python |
| 26 | +class Solution: |
| 27 | + def averageWaitingTime(self, customers: List[List[int]]) -> float: |
| 28 | + totalWait = 0 |
| 29 | + chefBusyUntil = 0 |
| 30 | + |
| 31 | + for x, y in customers: |
| 32 | + if x < chefBusyUntil: |
| 33 | + totalWait += chefBusyUntil - x |
| 34 | + else: |
| 35 | + chefBusyUntil = x |
| 36 | + totalWait += y |
| 37 | + chefBusyUntil += y |
| 38 | + |
| 39 | + return totalWait / len(customers) |
| 40 | +``` |
| 41 | +- given test cases pass |
| 42 | +- `customers = [[5,2],[5,4],[10,3],[20,1],[21,10000],[21, 5]]`: pass |
| 43 | +- `customers = [[1, 1000]]`: pass |
| 44 | +- Ok, this seems fine...submitting... |
| 45 | + |
| 46 | + |
| 47 | + |
| 48 | +solved! |
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