Price list behind API: Difference between revisions
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pmax = mc[0] |
pmax = mc[0] |
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pcount = mc[1] |
pcount = mc[1] |
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if (pcount == 0) Fiber.abort("Price list from %(pmin) has too many with same price.") |
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res.add([pmin, pmax, pcount]) |
res.add([pmin, pmax, pcount]) |
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} |
} |
Revision as of 12:29, 30 November 2020
There is a list of around 100_000 prices in the range £0 to £100_000, expressed
in whole £, (no pence); and prices may be duplicated.
The API allows access to the maximum item price via
function get_max_price()
; and the number of items equal-to and between two
given price points via function get_prange_count(pricemin, pricemax)
.
Assume that for the purposes of testing, you have access to the actual number of priced items to split.
- Task
- Write functions to randomly generate around 100K prices and provide the
get_prange_count
andget_max_price
API calls. - Write functions to provide non-overlapping min and max price ranges that provide product counts where most are close to, but no more than, 5_000.
- Ensure that all priced items are covered by all the ranges of prices shown
- Show ascending price ranges and the number of items covered by each range.
- Show output from a sample run here.
Go
<lang go>package main
import (
"fmt" "math" "math/rand" "time"
)
var minDelta = 1.0
func getMaxPrice(prices []float64) float64 {
max := prices[0] for i := 1; i < len(prices); i++ { if prices[i] > max { max = prices[i] } } return max
}
func getPRangeCount(prices []float64, min, max float64) int {
count := 0 for _, price := range prices { if price >= min && price <= max { count++ } } return count
}
func get5000(prices []float64, min, max float64, n int) (float64, int) {
count := getPRangeCount(prices, min, max) delta := (max - min) / 2 for count != n && delta >= minDelta/2 { if count > n { max -= delta } else { max += delta } max = math.Floor(max) count = getPRangeCount(prices, min, max) delta /= 2 } return max, count
}
func getAll5000(prices []float64, min, max float64, n int) [][3]float64 {
pmax, pcount := get5000(prices, min, max, n) res := [][3]float64Template:Min, pmax, float64(pcount) for pmax < max { pmin := pmax + 1 pmax, pcount = get5000(prices, pmin, max, n) res = append(res, [3]float64{pmin, pmax, float64(pcount)}) } return res
}
func main() {
rand.Seed(time.Now().UnixNano()) numPrices := 99000 + rand.Intn(2001) maxPrice := 1e5 prices := make([]float64, numPrices) // list of prices for i := 0; i < numPrices; i++ { prices[i] = float64(rand.Intn(int(maxPrice) + 1)) } actualMax := getMaxPrice(prices) fmt.Println("Using", numPrices, "items with prices from 0 to", actualMax, "\b:") res := getAll5000(prices, 0, actualMax, 5000) fmt.Println("Split into", len(res), "bins of approx 5000 elements:") total := 0 for _, r := range res { min := int(r[0]) tmx := r[1] if tmx > actualMax { tmx = actualMax } max := int(tmx) cnt := int(r[2]) total += cnt fmt.Printf(" From %6d to %6d with %4d items\n", min, max, cnt) } if total != numPrices { fmt.Println("Something went wrong - grand total of", total, "doesn't equal", numPrices, "\b!") }
}</lang>
- Output:
Using 99784 items with prices from 0 to 99999 : Split into 20 bins of approx 5000 elements: From 0 to 5061 with 4997 items From 5062 to 10031 with 5000 items From 10032 to 15091 with 5000 items From 15092 to 20114 with 5000 items From 20115 to 25141 with 5000 items From 25142 to 30206 with 4997 items From 30207 to 35291 with 5000 items From 35292 to 40333 with 4999 items From 40334 to 45451 with 4999 items From 45452 to 50422 with 4998 items From 50423 to 55355 with 4997 items From 55356 to 60268 with 4997 items From 60269 to 65240 with 5000 items From 65241 to 70193 with 4999 items From 70194 to 75272 with 4998 items From 75273 to 80154 with 5000 items From 80155 to 85218 with 5000 items From 85219 to 90120 with 4996 items From 90121 to 95102 with 4998 items From 95103 to 99999 with 4809 items
Julia
<lang julia># Sample price generation const price_list_size = rand(99000:100999) const price_list = rand(0:99999, price_list_size) const delta_price = 1 # Minimum difference between any two different prices.
""" The API provides these two """ get_prange_count(startp, endp) = sum([startp <= r <= endp for r in price_list]) get_max_price() = maximum(price_list)
""" Binary search for num items between mn and mx, adjusting mx """ function get_5k(mn=0, mx=get_max_price(), num=5_000)
count = get_prange_count(mn, mx) delta_mx = (mx - mn) / 2 while count != num && delta_mx >= delta_price / 2 mx += (count > num ? -delta_mx : +delta_mx) mx = floor(mx) count, delta_mx = get_prange_count(mn, mx), delta_mx / 2 end return mx, count
end
""" Get all non-overlapping ranges """ function get_all_5k(mn=0, mx=get_max_price(), num=5_000)
partmax, partcount = get_5k(mn, mx, num) result = [(mn, partmax, partcount)] while partmax < mx partmin = partmax + delta_price partmax, partcount = get_5k(partmin, mx, num) @assert(partcount > 0, "pricelist from $partmin has too many same price") push!(result, (partmin, partmax, partcount)) end return result
end
function testpricelist()
println("Using $price_list_size random prices from 0 to $(get_max_price()).") result = get_all_5k() println("Splits into $(length(result)) bins of approximately 5000 elements.") for (mn, mx, count) in result println(" From $(Float32(mn)) ... $(Float32(mx)) with $count items.") end if length(price_list) != sum([x[3] for x in result]) print("\nWhoops! Some items missing.") end
end
testpricelist()
</lang>
- Output:
Using 100299 random prices from 0 to 99990. Splits into 21 bins of approximately 5000 elements. From 0.0 ... 4911.0 with 4998 items. From 4912.0 ... 9832.0 with 5000 items. From 9833.0 ... 14841.0 with 5000 items. From 14842.0 ... 19756.0 with 4999 items. From 19757.0 ... 24782.0 with 4994 items. From 24783.0 ... 29751.0 with 4999 items. From 29752.0 ... 34655.0 with 5000 items. From 34656.0 ... 39748.0 with 5000 items. From 39749.0 ... 44819.0 with 4999 items. From 44820.0 ... 49908.0 with 5000 items. From 49909.0 ... 54898.0 with 4999 items. From 54899.0 ... 59700.0 with 4999 items. From 59701.0 ... 64767.0 with 4999 items. From 64768.0 ... 69824.0 with 4999 items. From 69825.0 ... 74765.0 with 4999 items. From 74766.0 ... 79654.0 with 4999 items. From 79655.0 ... 84674.0 with 5000 items. From 84675.0 ... 89602.0 with 4999 items. From 89603.0 ... 94715.0 with 5000 items. From 94716.0 ... 99666.0 with 4997 items. From 99667.0 ... 100309.0 with 320 items.
Phix
Note that defaulted arguments of the form mx=get_max_price() are not currently supported, hence a slightly hacky workaround.
If you defined constant mp = get_max_price(), then mx=mp style parameter defaulting would be fine.
<lang Phix>constant price_list_size = 99_000 + rand(2_001) - 1,
price_list = sq_sub(sq_rand(repeat(100_000,price_list_size)),1), delta_price = 1 -- Minimum difference between any two different prices.
function get_prange_count(integer startp, endp)
return length(filter(price_list,"in",{startp,endp},"[]"))
end function
function get_max_price()
return max(price_list)
end function
function get_5k(integer mn=0, mx=-1, num=5_000)
if mx=-1 then mx = get_max_price() end if -- Binary search for num items between mn and mx, adjusting mx integer count = get_prange_count(mn, mx) atom delta_mx = (mx - mn) / 2 while count != num and delta_mx >= delta_price / 2 do mx = floor(mx + iff(count > num ? -delta_mx : +delta_mx)) {count, delta_mx} = {get_prange_count(mn, mx), delta_mx / 2} end while return {mx, count}
end function
function get_all_5k(integer mn=0, mx=-1, num=5_000)
if mx=-1 then mx = get_max_price() end if -- Get all non-overlapping ranges integer {partmax, partcount} = get_5k(mn, mx, num) sequence result = Template:Mn, partmax, partcount while partmax < mx do integer partmin = partmax + delta_price {partmax, partcount} = get_5k(partmin, mx, num) result = append(result,{partmin, partmax, partcount}) end while return result
end function
printf(1,"Using %d random prices from 0 to %d\n",{price_list_size,get_max_price()}) sequence result = get_all_5k() printf(1,"Splits into %d bins of approx 5000 elements\n",{length(result)}) for i=1 to length(result) do
printf(1," From %8.1f ... %8.1f with %d items.\n",result[i])
end for if length(price_list) != sum(vslice(result,3)) then
printf(1,"\nWhoops! Some items missing:\n")
end if</lang>
- Output:
Using 99714 random prices from 0 to 99999 Splits into 20 bins of approx 5000 elements From 0.0 ... 4977.0 with 5000 items. From 4978.0 ... 10019.0 with 4999 items. From 10020.0 ... 15114.0 with 4999 items. From 15115.0 ... 19987.0 with 4998 items. From 19988.0 ... 25088.0 with 4996 items. From 25089.0 ... 30080.0 with 4995 items. From 30081.0 ... 35117.0 with 5000 items. From 35118.0 ... 40081.0 with 4999 items. From 40082.0 ... 45080.0 with 5000 items. From 45081.0 ... 50181.0 with 5000 items. From 50182.0 ... 55223.0 with 5000 items. From 55224.0 ... 60271.0 with 5000 items. From 60272.0 ... 65102.0 with 4999 items. From 65103.0 ... 70140.0 with 5000 items. From 70141.0 ... 75195.0 with 4997 items. From 75196.0 ... 80203.0 with 4998 items. From 80204.0 ... 85210.0 with 4999 items. From 85211.0 ... 90182.0 with 5000 items. From 90183.0 ... 95268.0 with 4999 items. From 95269.0 ... 104722.0 with 4736 items.
Python
<lang python>import random
- %%Sample price generation
price_list_size = random.choice(range(99_000, 101_000)) price_list = random.choices(range(100_000), k=price_list_size)
delta_price = 1 # Minimum difference between any two different prices.
- %% API
def get_prange_count(startp, endp):
return len([r for r in price_list if startp <= r <= endp])
def get_max_price():
return max(price_list)
- %% Solution
def get_5k(mn=0, mx=get_max_price(), num=5_000):
"Binary search for num items between mn and mx, adjusting mx" count = get_prange_count(mn, mx) delta_mx = (mx - mn) / 2 while count != num and delta_mx >= delta_price / 2: mx += -delta_mx if count > num else +delta_mx mx = mx // 1 # Floor count, delta_mx = get_prange_count(mn, mx), delta_mx / 2 return mx, count
def get_all_5k(mn=0, mx=get_max_price(), num=5_000):
"Get all non-overlapping ranges" partmax, partcount = get_5k(mn, mx, num) result = [(mn, partmax, partcount)] while partmax < mx: partmin = partmax + delta_price partmax, partcount = get_5k(partmin, mx, num) assert partcount > 0, \ f"price_list from {partmin} with too many of the same price" result.append((partmin, partmax, partcount)) return result
if __name__ == '__main__':
print(f"Using {price_list_size} random prices from 0 to {get_max_price()}") result = get_all_5k() print(f"Splits into {len(result)} bins of approx 5000 elements") for mn, mx, count in result: print(f" From {mn:8.1f} ... {mx:8.1f} with {count} items.")
if len(price_list) != sum(count for mn, mx, count in result): print("\nWhoops! Some items missing:")</lang>
- Output:
Using 99838 random prices from 0 to 99999 Splits into 20 bins of approx 5000 elements From 0.0 ... 4876.0 with 4999 items. From 4877.0 ... 9973.0 with 4997 items. From 9974.0 ... 14954.0 with 4999 items. From 14955.0 ... 20041.0 with 4997 items. From 20042.0 ... 25132.0 with 4999 items. From 25133.0 ... 30221.0 with 5000 items. From 30222.0 ... 35313.0 with 5000 items. From 35314.0 ... 40263.0 with 5000 items. From 40264.0 ... 45249.0 with 4997 items. From 45250.0 ... 50264.0 with 5000 items. From 50265.0 ... 55251.0 with 5000 items. From 55252.0 ... 60301.0 with 4997 items. From 60302.0 ... 65239.0 with 5000 items. From 65240.0 ... 70220.0 with 4998 items. From 70221.0 ... 75193.0 with 4999 items. From 75194.0 ... 80229.0 with 4996 items. From 80230.0 ... 85191.0 with 4997 items. From 85192.0 ... 90214.0 with 5000 items. From 90215.0 ... 95249.0 with 4999 items. From 95250.0 ... 104742.0 with 4864 items.
Wren
<lang ecmascript>import "random" for Random import "/math" for Nums import "/fmt" for Fmt
var rand = Random.new() var minDelta = 1
var getMaxPrice = Fn.new { |prices| Nums.max(prices) }
var getPrangeCount = Fn.new { |prices, min, max| prices.count { |p| p >= min && p <= max } }
var get5000 = Fn.new { |prices, min, max, n|
var count = getPrangeCount.call(prices, min, max) var delta = (max - min) / 2 while (count != n && delta >= minDelta/2) { max = ((count > n) ? max-delta : max+delta).floor count = getPrangeCount.call(prices, min, max) delta = delta / 2 } return [max, count]
}
var getAll5000 = Fn.new { |prices, min, max, n|
var mc = get5000.call(prices, min, max, n) var pmax = mc[0] var pcount = mc[1] var res = min, pmax, pcount while (pmax < max) { var pmin = pmax + 1 mc = get5000.call(prices, pmin, max, n) pmax = mc[0] pcount = mc[1] if (pcount == 0) Fiber.abort("Price list from %(pmin) has too many with same price.") res.add([pmin, pmax, pcount]) } return res
} var numPrices = rand.int(99000, 101001) var maxPrice = 1e5 var prices = List.filled(numPrices, 0) // list of prices for (i in 1..numPrices) prices[i-1] = rand.int(maxPrice + 1) var actualMax = getMaxPrice.call(prices) System.print("Using %(numPrices) items with prices from 0 to %(actualMax):") var res = getAll5000.call(prices, 0, actualMax, 5000) System.print("Split into %(res.count) bins of approx 5000 elements:") var total = 0 for (r in res) {
var min = r[0] var max = r[1] if (max > actualMax) max = actualMax var cnt = r[2] total = total + cnt Fmt.print(" From $6d to $6d with $4d items", min, max, cnt)
} if (total != numPrices) {
System.print("Something went wrong - grand total of %(total) doesn't equal %(numPrices)!")
}</lang>
- Output:
Sample run:
Using 99756 items with prices from 0 to 99998: Split into 20 bins of approx 5000 elements: From 0 to 4964 with 5000 items From 4965 to 9992 with 5000 items From 9993 to 15063 with 5000 items From 15064 to 20130 with 5000 items From 20131 to 25063 with 4998 items From 25064 to 30014 with 4998 items From 30015 to 35002 with 5000 items From 35003 to 40030 with 5000 items From 40031 to 45058 with 5000 items From 45059 to 50199 with 4999 items From 50200 to 55133 with 4999 items From 55134 to 60139 with 4997 items From 60140 to 65097 with 5000 items From 65098 to 69972 with 4999 items From 69973 to 74932 with 5000 items From 74933 to 80041 with 5000 items From 80042 to 85214 with 5000 items From 85215 to 90241 with 4999 items From 90242 to 95353 with 5000 items From 95354 to 99998 with 4767 items