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A growth analytics team needs to identify customers whose yearly purchase spend keeps rising without any stagnation or decline.
Table: Orders
Yearly total definition: For each customer and calendar year, yearly_total is SUM(price) for orders in that year.
Evaluation window per customer:
Qualification rule: A customer is valid only if yearly totals are strictly increasing across every adjacent year pair in the interval. That means for each year y in the interval (except the last): total(y + 1) > total(y)
Task: Return all qualifying customer IDs.
Supported submission environments:
Orders:
| order_id | customer_id | order_date | price |
|----------|-------------|-------------|-------|
| 1 | 1 | 2019-07-01 | 1100 |
| 2 | 1 | 2019-11-01 | 1200 |
| 3 | 1 | 2020-05-26 | 3000 |
| 4 | 1 | 2021-08-31 | 3100 |
| 5 | 1 | 2022-12-07 | 4700 |
| 6 | 2 | 2015-01-01 | 700 |
| 7 | 2 | 2017-11-07 | 1000 |
| 8 | 3 | 2017-01-01 | 900 |
| 9 | 3 | 2018-11-07 | 900 |[
{"customer_id":1}
]Explanation
Customer 1 has yearly totals 2300 < 3000 < 3100 < 4700, so they qualify. Customer 2 fails because year 2016 is missing and therefore contributes 0 between 700 and 1000. Customer 3 fails because 900 is not strictly less than 900.
Orders:
| order_id | customer_id | order_date | price |
|----------|-------------|-------------|-------|
| 10 | 10 | 2020-03-05 | 400 |
| 11 | 10 | 2020-10-20 | 600 |
| 12 | 10 | 2021-07-04 | 1001 |
| 13 | 11 | 2020-02-14 | 500 |
| 14 | 11 | 2022-08-01 | 900 |
| 15 | 12 | 2021-11-11 | 400 |[
{"customer_id":10},
{"customer_id":12}
]Explanation
Customer 10 rises from 1000 to 1001 and qualifies. Customer 11 fails because year 2021 has zero spend between first and last years. Customer 12 has only one year and therefore has no violating adjacent pair.
Orders:
| order_id | customer_id | order_date | price |
|----------|-------------|-------------|-------|
| 20 | 20 | 2018-01-02 | 100 |
| 21 | 20 | 2019-02-03 | 200 |
| 22 | 20 | 2020-03-04 | 400 |
| 23 | 21 | 2018-05-05 | 150 |
| 24 | 21 | 2019-06-06 | 150 |
| 25 | 22 | 2021-12-31 | 900 |[
{"customer_id":20},
{"customer_id":22}
]Explanation
Customer 20 is strictly increasing each year. Customer 21 has equal totals in 2018 and 2019, so strict growth is violated. Customer 22 appears in one year only and qualifies.
Constraints