Order book 
Simulate a sell-side order book and calculate the cost of a final purchase as fast as possible.
Input
1,000,000 order updates on STDIN, one per line:
+ <price> <size>– add a new sell order- <position>– delete the order at the given position= <size>– buy<size>shares from the top of the order book
After all updates are processed, buy 1,000 shares from the top of the order book.
Output
Print the total cost of the final 1,000-share purchase to STDOUT.
Order Book Rules
Orders are sorted by price ascending (lower is better). Orders at the same price are sorted by arrival time (earlier first). Position 0 is the best (lowest-price) offer.
The = (buy) operation consumes shares starting from position 0. If an order is fully consumed, it is removed from the book.
Example
| Input | Order book state |
|---|---|
+ 1137 100 |
(1137,100) |
+ 1130 10 |
(1130,10), (1137,100) |
+ 1130 50 |
(1130,10), (1130,50), (1137,100) |
- 0 |
(1130,50), (1137,100) |
+ 1150 200 |
(1130,50), (1137,100), (1150,200) |
= 200 |
(1150,150) |
Total cost of the last buy: 50 * 1130 + 100 * 1137 + 50 * 1150.
Josu San MartinSource Code
Source code access is restricted. Log in to request access.
Challenge History
| Date | Challenger | Cost | Type | Status |
|---|---|---|---|---|
| Sep 15, 2026 12:24 | Andrew Epstein | 10.00 | Custom | Solution Broken |
Run Statistics
| # | Date | Score | Wall Time | CPU User | CPU System | Memory | Error | |
|---|---|---|---|---|---|---|---|---|
| 1 | Sep 15, 2026 12:30 | 0 | 10,724,648 | 783,000 | 0 | 20,480 | No answer to stdout. Died or killed? | |
| 2 | Dec 21, 2025 19:01 | 34,590 | 44,171,089 | 19,059,000 | 1,003,000 | 2,269,184 | ||
| 3 | Dec 21, 2025 19:01 | 34,695 | 39,649,070 | 18,111,000 | 2,012,000 | 2,486,272 | ||
| 4 | Dec 21, 2025 19:01 | 34,753 | 40,747,499 | 18,142,000 | 2,015,000 | 2,506,752 | ||
| 5 | Dec 21, 2025 19:01 | 34,912 | 44,318,736 | 19,237,000 | 1,012,000 | 2,453,504 | ||
| 6 | Dec 21, 2025 19:03 | 34,919 | 47,457,318 | 20,253,000 | 0 | 2,490,368 | ||
| 7 | Dec 21, 2025 19:03 | 35,010 | 43,353,985 | 19,291,000 | 1,015,000 | 2,510,848 | ||
| 8 | Dec 21, 2025 19:02 | 35,040 | 42,770,227 | 19,307,000 | 1,016,000 | 2,437,120 | ||
| 9 | Dec 21, 2025 19:02 | 35,124 | 36,755,650 | 19,354,000 | 1,018,000 | 2,269,184 | ||
| 10 | Dec 21, 2025 19:02 | 35,214 | 48,425,389 | 19,403,000 | 1,021,000 | 2,478,080 | ||
| 11 | Dec 21, 2025 19:02 | 35,298 | 43,248,072 | 18,426,000 | 2,047,000 | 2,314,240 | ||
| 12 | Dec 21, 2025 19:03 | 35,390 | 43,220,134 | 19,500,000 | 1,026,000 | 2,510,848 | ||
| 13 | Dec 21, 2025 19:03 | 35,457 | 40,814,813 | 19,537,000 | 1,028,000 | 2,506,752 | ||
| 14 | Dec 22, 2025 04:20 | 35,483 | 40,206,905 | 19,551,000 | 1,029,000 | 2,469,888 | ||
| 15 | Dec 21, 2025 19:03 | 35,572 | 45,780,542 | 19,601,000 | 1,031,000 | 2,498,560 | ||
| 16 | Dec 21, 2025 19:01 | 35,633 | 53,057,277 | 20,667,000 | 0 | 2,457,600 | ||
| 17 | Dec 21, 2025 19:03 | 35,772 | 46,415,109 | 19,711,000 | 1,037,000 | 2,297,856 | ||
| 18 | Dec 21, 2025 19:02 | 36,045 | 46,002,933 | 18,915,000 | 1,991,000 | 2,457,600 | ||
| 19 | Dec 21, 2025 19:01 | 36,071 | 46,349,398 | 19,925,000 | 996,000 | 2,478,080 | ||
| 20 | Dec 21, 2025 19:03 | 36,321 | 44,849,980 | 20,063,000 | 1,003,000 | 2,502,656 | ||
| 21 | Dec 21, 2025 19:01 | 36,359 | 50,515,139 | 20,084,000 | 1,004,000 | 2,416,640 | ||
| 22 | Dec 21, 2025 19:03 | 36,400 | 41,344,674 | 19,102,000 | 2,010,000 | 2,445,312 | ||
| 23 | Dec 21, 2025 19:03 | 36,402 | 44,222,187 | 19,103,000 | 2,010,000 | 2,465,792 | ||
| 24 | Dec 21, 2025 19:02 | 36,419 | 46,525,697 | 19,112,000 | 2,011,000 | 2,441,216 | ||
| 25 | Dec 21, 2025 19:03 | 36,429 | 52,937,751 | 19,117,000 | 2,012,000 | 2,351,104 | ||
| 26 | Dec 21, 2025 19:03 | 36,493 | 46,383,654 | 19,151,000 | 2,015,000 | 2,461,696 | ||
| 27 | Dec 21, 2025 19:02 | 36,519 | 37,019,864 | 19,164,000 | 2,017,000 | 2,301,952 | ||
| 28 | Dec 23, 2025 04:16 | 36,588 | 43,283,443 | 20,211,000 | 1,010,000 | 2,506,752 | ||
| 29 | Dec 21, 2025 19:03 | 36,626 | 47,727,271 | 19,220,000 | 2,023,000 | 2,457,600 | ||
| 30 | Dec 21, 2025 19:03 | 36,628 | 43,674,391 | 19,221,000 | 2,023,000 | 2,383,872 | ||
| 31 | Dec 21, 2025 19:02 | 36,714 | 43,301,627 | 20,280,000 | 1,014,000 | 2,465,792 | ||
| 32 | Dec 21, 2025 19:02 | 36,834 | 43,577,470 | 20,347,000 | 1,017,000 | 2,338,816 | ||
| 33 | Dec 21, 2025 19:02 | 36,847 | 45,033,326 | 19,336,000 | 2,035,000 | 2,453,504 | ||
| 34 | Dec 21, 2025 19:02 | 36,876 | 46,483,831 | 20,370,000 | 1,018,000 | 2,428,928 | ||
| 35 | Dec 21, 2025 19:02 | 36,884 | 47,870,769 | 20,375,000 | 1,018,000 | 2,318,336 | ||
| 36 | Dec 23, 2025 04:16 | 36,884 | 55,022,700 | 21,393,000 | 0 | 2,412,544 | ||
| 37 | Dec 21, 2025 19:03 | 36,900 | 41,469,638 | 20,383,000 | 1,019,000 | 2,457,600 | ||
| 38 | Dec 21, 2025 19:02 | 36,910 | 40,125,003 | 21,408,000 | 0 | 2,506,752 | ||
| 39 | Dec 21, 2025 19:01 | 36,972 | 46,223,354 | 20,423,000 | 1,021,000 | 2,371,584 | ||
| 40 | Dec 21, 2025 19:02 | 36,988 | 47,182,248 | 20,432,000 | 1,021,000 | 2,424,832 | ||
| 41 | Dec 21, 2025 19:01 | 36,990 | 47,406,544 | 20,433,000 | 1,021,000 | 2,293,760 | ||
| 42 | Dec 23, 2025 04:16 | 37,010 | 47,323,475 | 20,444,000 | 1,022,000 | 2,330,624 | ||
| 43 | Dec 21, 2025 19:03 | 37,052 | 51,769,351 | 21,490,000 | 0 | 2,449,408 | ||
| 44 | Dec 22, 2025 04:20 | 37,090 | 44,588,226 | 20,488,000 | 1,024,000 | 2,506,752 | ||
| 45 | Dec 21, 2025 19:03 | 37,119 | 46,139,298 | 21,529,000 | 0 | 2,428,928 | ||
| 46 | Dec 21, 2025 19:01 | 37,147 | 45,679,067 | 21,545,000 | 0 | 2,281,472 | ||
| 47 | Dec 21, 2025 19:03 | 37,214 | 47,626,618 | 20,557,000 | 1,027,000 | 2,416,640 | ||
| 48 | Dec 21, 2025 19:02 | 37,224 | 43,987,112 | 20,562,000 | 1,028,000 | 2,490,368 | ||
| 49 | Dec 21, 2025 19:01 | 37,300 | 42,656,953 | 20,604,000 | 1,030,000 | 2,412,544 | ||
| 50 | Dec 22, 2025 04:20 | 37,305 | 42,618,143 | 20,607,000 | 1,030,000 | 2,424,832 | ||
| 51 | Dec 21, 2025 19:03 | 37,314 | 43,381,110 | 20,612,000 | 1,030,000 | 2,412,544 | ||
| 52 | Dec 21, 2025 19:01 | 38,067 | 45,845,391 | 21,076,000 | 1,003,000 | 2,465,792 |