Largest Square Submatrix of all 1's 
Find the largest square submatrix consisting entirely of 1s as fast as possible.
Input
A 10,000 x 10,000 matrix of uint8 values (0 or 1) on STDIN.
0, 1, 0, 1, 1
0, 1, 1, 1, 1
0, 0, 1, 0, 0
1, 0, 1, 1, 0
Output
Print the side length of the largest all-ones square submatrix to STDOUT. The answer is guaranteed to be greater than 1.
For the example above, the output is:
2
Source Code
Source code access is restricted. Log in to request access.
Challenge History
| Date | Challenger | Cost | Type | Status |
|---|---|---|---|---|
| May 17, 2026 14:58 | M-Rochat | 10.00 | Custom | Solution Broken |
Run Statistics
| # | Date | Score | Wall Time | CPU User | CPU System | Memory | Error | |
|---|---|---|---|---|---|---|---|---|
| 1 | May 17, 2026 15:30 | 0 | 10,840,415 | 985,000 | 0 | 2,117,632 | expected "253", got "100 " | |
| 2 | May 17, 2026 15:30 | 0 | 10,852,245 | 934,000 | 0 | 2,117,632 | expected "253", got "100 " | |
| 3 | May 17, 2026 15:30 | 0 | 8,368,960 | 808,000 | 0 | 24,576 | expected "253", got "100 " | |
| 4 | Jan 5, 2026 04:33 | 3,085 | 18,077,508 | 1,234,000 | 0 | 2,453,504 | ||
| 5 | Jan 5, 2026 04:33 | 3,333 | 16,505,202 | 1,333,000 | 0 | 2,449,408 | ||
| 6 | Jan 4, 2026 06:29 | 3,508 | 22,132,100 | 1,403,000 | 0 | 2,449,408 | ||
| 7 | Jan 4, 2026 06:33 | 3,570 | 16,743,481 | 1,428,000 | 0 | 2,445,312 | ||
| 8 | Jan 5, 2026 04:39 | 3,610 | 19,585,791 | 1,444,000 | 0 | 2,453,504 | ||
| 9 | Jan 4, 2026 06:34 | 3,620 | 15,705,291 | 1,448,000 | 0 | 2,441,216 | ||
| 10 | Jan 4, 2026 06:33 | 3,628 | 18,688,229 | 0 | 1,451,000 | 2,449,408 | ||
| 11 | Jan 4, 2026 06:33 | 3,630 | 23,807,717 | 1,452,000 | 0 | 2,453,504 | ||
| 12 | Jan 4, 2026 06:33 | 3,633 | 15,955,035 | 1,453,000 | 0 | 2,449,408 | ||
| 13 | Jan 17, 2026 17:21 | 3,633 | 16,914,723 | 1,453,000 | 0 | 2,449,408 | ||
| 14 | Jan 4, 2026 06:29 | 3,638 | 15,569,787 | 1,455,000 | 0 | 2,445,312 | ||
| 15 | Jan 18, 2026 01:10 | 3,640 | 17,200,266 | 1,456,000 | 0 | 2,453,504 | ||
| 16 | Jan 18, 2026 01:10 | 3,643 | 20,661,850 | 1,457,000 | 0 | 2,449,408 | ||
| 17 | Jan 4, 2026 06:38 | 3,660 | 12,850,383 | 0 | 1,464,000 | 2,453,504 | ||
| 18 | Jan 18, 2026 01:10 | 3,660 | 19,530,838 | 1,464,000 | 0 | 2,449,408 | ||
| 19 | Jan 17, 2026 17:19 | 3,678 | 23,338,714 | 1,471,000 | 0 | 2,445,312 | ||
| 20 | Jan 4, 2026 06:33 | 3,685 | 16,994,346 | 1,474,000 | 0 | 2,441,216 | ||
| 21 | Jan 4, 2026 06:33 | 3,685 | 21,829,931 | 1,474,000 | 0 | 2,445,312 | ||
| 22 | Jan 17, 2026 17:19 | 3,685 | 21,326,135 | 0 | 1,474,000 | 2,449,408 | ||
| 23 | Jan 17, 2026 17:19 | 3,690 | 16,942,943 | 1,476,000 | 0 | 2,453,504 | ||
| 24 | Jan 17, 2026 17:28 | 3,693 | 22,124,809 | 1,477,000 | 0 | 2,449,408 | ||
| 25 | Jan 4, 2026 06:33 | 3,700 | 17,966,671 | 1,480,000 | 0 | 2,445,312 | ||
| 26 | Jan 17, 2026 17:19 | 3,700 | 21,418,605 | 1,480,000 | 0 | 2,441,216 | ||
| 27 | Jan 18, 2026 01:16 | 3,705 | 19,379,195 | 1,482,000 | 0 | 2,453,504 | ||
| 28 | Jan 17, 2026 17:25 | 3,713 | 17,242,728 | 1,485,000 | 0 | 2,449,408 | ||
| 29 | Jan 5, 2026 04:39 | 3,720 | 13,409,486 | 1,488,000 | 0 | 2,449,408 | ||
| 30 | Jan 17, 2026 17:27 | 3,728 | 17,847,903 | 1,491,000 | 0 | 2,441,216 | ||
| 31 | Jan 5, 2026 04:39 | 3,733 | 14,227,806 | 1,493,000 | 0 | 2,445,312 | ||
| 32 | Jan 18, 2026 01:16 | 3,733 | 19,369,535 | 0 | 1,493,000 | 2,453,504 | ||
| 33 | Jan 17, 2026 17:27 | 3,735 | 22,031,942 | 1,494,000 | 0 | 2,453,504 | ||
| 34 | Jan 17, 2026 17:28 | 3,735 | 23,145,434 | 1,494,000 | 0 | 2,449,408 | ||
| 35 | Jan 4, 2026 06:33 | 3,738 | 16,439,064 | 1,495,000 | 0 | 2,445,312 | ||
| 36 | Jan 18, 2026 01:10 | 3,740 | 16,693,943 | 0 | 1,496,000 | 2,445,312 | ||
| 37 | Jan 17, 2026 17:21 | 3,743 | 17,570,491 | 0 | 1,497,000 | 2,445,312 | ||
| 38 | Jan 4, 2026 06:37 | 3,745 | 14,375,517 | 1,498,000 | 0 | 2,449,408 | ||
| 39 | Jan 5, 2026 02:27 | 3,748 | 17,377,619 | 1,499,000 | 0 | 2,445,312 | ||
| 40 | Jan 4, 2026 06:29 | 3,750 | 16,305,360 | 0 | 1,500,000 | 2,535,424 | ||
| 41 | Jan 5, 2026 04:39 | 3,753 | 19,979,888 | 0 | 1,501,000 | 2,449,408 | ||
| 42 | Jan 17, 2026 17:21 | 3,753 | 18,582,507 | 0 | 1,501,000 | 2,441,216 | ||
| 43 | Jan 4, 2026 06:35 | 3,758 | 18,736,369 | 0 | 1,503,000 | 2,445,312 | ||
| 44 | Jan 17, 2026 17:27 | 3,758 | 18,818,392 | 1,503,000 | 0 | 2,449,408 | ||
| 45 | Jan 17, 2026 17:19 | 3,760 | 19,920,977 | 1,504,000 | 0 | 2,441,216 | ||
| 46 | Jan 18, 2026 01:10 | 3,765 | 22,272,042 | 1,506,000 | 0 | 2,441,216 | ||
| 47 | Jan 4, 2026 06:35 | 3,768 | 17,601,441 | 1,507,000 | 0 | 2,445,312 | ||
| 48 | Jan 5, 2026 02:28 | 3,768 | 14,757,236 | 1,507,000 | 0 | 2,535,424 | ||
| 49 | Jan 5, 2026 04:39 | 3,768 | 16,371,870 | 0 | 1,507,000 | 2,441,216 | ||
| 50 | Jan 18, 2026 01:10 | 3,768 | 18,304,587 | 1,507,000 | 0 | 2,445,312 | ||
| 51 | Jan 18, 2026 01:16 | 3,768 | 18,939,229 | 1,507,000 | 0 | 2,445,312 | ||
| 52 | Jan 17, 2026 17:19 | 3,770 | 17,206,506 | 1,508,000 | 0 | 2,449,408 | ||
| 53 | Jan 17, 2026 17:21 | 3,770 | 17,833,114 | 0 | 1,508,000 | 2,449,408 | ||
| 54 | Jan 17, 2026 17:25 | 3,775 | 21,115,111 | 1,510,000 | 0 | 2,535,424 | ||
| 55 | Jan 17, 2026 17:25 | 3,775 | 18,609,766 | 0 | 1,510,000 | 2,453,504 | ||
| 56 | Jan 4, 2026 06:35 | 3,780 | 17,472,032 | 1,512,000 | 0 | 2,445,312 | ||
| 57 | Jan 4, 2026 06:34 | 3,783 | 22,541,311 | 1,513,000 | 0 | 2,441,216 | ||
| 58 | Jan 17, 2026 17:21 | 3,783 | 12,858,618 | 1,513,000 | 0 | 2,445,312 | ||
| 59 | Jan 17, 2026 17:19 | 3,785 | 19,721,461 | 0 | 1,514,000 | 2,453,504 | ||
| 60 | Jan 17, 2026 17:21 | 3,785 | 16,225,882 | 1,514,000 | 0 | 2,445,312 | ||
| 61 | Jan 17, 2026 17:21 | 3,785 | 14,967,961 | 1,514,000 | 0 | 2,535,424 | ||
| 62 | Jan 4, 2026 06:36 | 3,788 | 14,685,693 | 0 | 1,515,000 | 2,445,312 | ||
| 63 | Jan 5, 2026 02:27 | 3,788 | 19,539,834 | 1,515,000 | 0 | 2,445,312 | ||
| 64 | Jan 5, 2026 04:33 | 3,788 | 19,962,073 | 1,515,000 | 0 | 2,449,408 | ||
| 65 | Jan 4, 2026 06:37 | 3,790 | 19,516,537 | 1,516,000 | 0 | 2,449,408 | ||
| 66 | Jan 18, 2026 01:16 | 3,790 | 18,222,323 | 0 | 1,516,000 | 2,445,312 | ||
| 67 | Jan 4, 2026 06:36 | 3,793 | 17,188,370 | 1,517,000 | 0 | 2,441,216 | ||
| 68 | Jan 17, 2026 17:21 | 3,793 | 16,048,618 | 1,517,000 | 0 | 2,535,424 | ||
| 69 | Jan 4, 2026 06:33 | 3,795 | 22,792,577 | 1,518,000 | 0 | 2,449,408 | ||
| 70 | Jan 4, 2026 06:33 | 3,798 | 19,253,284 | 1,519,000 | 0 | 2,535,424 | ||
| 71 | Jan 17, 2026 17:28 | 3,798 | 17,063,728 | 1,519,000 | 0 | 2,449,408 | ||
| 72 | Jan 17, 2026 17:28 | 3,800 | 22,962,051 | 1,520,000 | 0 | 2,445,312 | ||
| 73 | Jan 17, 2026 17:28 | 3,800 | 14,855,162 | 0 | 1,520,000 | 2,449,408 | ||
| 74 | Jan 18, 2026 01:10 | 3,800 | 18,255,030 | 1,520,000 | 0 | 2,445,312 | ||
| 75 | Jan 4, 2026 06:33 | 3,805 | 22,996,064 | 1,522,000 | 0 | 2,453,504 | ||
| 76 | Jan 18, 2026 01:10 | 3,805 | 22,664,972 | 1,522,000 | 0 | 2,453,504 | ||
| 77 | Jan 17, 2026 17:19 | 3,808 | 18,343,046 | 1,523,000 | 0 | 2,445,312 | ||
| 78 | Jan 4, 2026 06:33 | 3,810 | 19,528,443 | 1,524,000 | 0 | 2,453,504 | ||
| 79 | Jan 4, 2026 06:33 | 3,810 | 16,736,418 | 1,524,000 | 0 | 2,445,312 | ||
| 80 | Jan 18, 2026 01:16 | 3,818 | 16,187,168 | 1,527,000 | 0 | 2,535,424 | ||
| 81 | Jan 5, 2026 02:28 | 3,820 | 18,611,306 | 1,528,000 | 0 | 2,445,312 | ||
| 82 | Jan 4, 2026 06:33 | 3,823 | 13,361,655 | 1,529,000 | 0 | 2,453,504 | ||
| 83 | Jan 17, 2026 17:20 | 3,823 | 14,719,388 | 1,529,000 | 0 | 2,441,216 | ||
| 84 | Jan 17, 2026 17:28 | 3,823 | 14,932,002 | 1,529,000 | 0 | 2,441,216 | ||
| 85 | Jan 4, 2026 06:37 | 3,825 | 15,104,245 | 1,530,000 | 0 | 2,535,424 | ||
| 86 | Jan 17, 2026 17:20 | 3,830 | 17,098,712 | 1,532,000 | 0 | 2,449,408 | ||
| 87 | Jan 18, 2026 01:10 | 3,830 | 17,914,668 | 1,532,000 | 0 | 2,449,408 | ||
| 88 | Jan 4, 2026 06:33 | 3,833 | 18,197,365 | 0 | 1,533,000 | 2,445,312 | ||
| 89 | Jan 17, 2026 17:25 | 3,838 | 15,607,869 | 0 | 1,535,000 | 2,457,600 | ||
| 90 | Jan 18, 2026 01:10 | 3,845 | 21,147,293 | 1,538,000 | 0 | 2,449,408 | ||
| 91 | Jan 17, 2026 17:25 | 3,855 | 17,754,329 | 1,542,000 | 0 | 2,449,408 | ||
| 92 | Jan 5, 2026 04:39 | 3,863 | 17,166,296 | 1,545,000 | 0 | 2,445,312 | ||
| 93 | Jan 18, 2026 01:10 | 3,878 | 24,736,856 | 1,551,000 | 0 | 2,445,312 | ||
| 94 | Jan 18, 2026 01:10 | 3,878 | 17,578,161 | 1,551,000 | 0 | 2,449,408 | ||
| 95 | Jan 5, 2026 02:28 | 3,885 | 19,572,312 | 1,554,000 | 0 | 2,449,408 | ||
| 96 | Jan 17, 2026 17:19 | 3,893 | 16,650,579 | 1,557,000 | 0 | 2,535,424 | ||
| 97 | Jan 5, 2026 02:27 | 3,905 | 16,239,338 | 0 | 1,562,000 | 2,449,408 | ||
| 98 | Jan 4, 2026 06:35 | 3,913 | 18,878,361 | 1,565,000 | 0 | 2,449,408 | ||
| 99 | Jan 17, 2026 17:20 | 3,928 | 18,620,169 | 1,571,000 | 0 | 2,449,408 | ||
| 100 | Jan 4, 2026 06:38 | 3,945 | 22,291,581 | 1,578,000 | 0 | 2,445,312 | ||
| 101 | Jan 4, 2026 06:29 | 3,948 | 18,270,945 | 1,579,000 | 0 | 2,445,312 | ||
| 102 | Jan 4, 2026 06:34 | 3,985 | 19,419,351 | 1,594,000 | 0 | 2,441,216 | ||
| 103 | Jan 17, 2026 17:21 | 4,000 | 17,489,626 | 1,600,000 | 0 | 2,453,504 | ||
| 104 | Jan 4, 2026 06:35 | 4,005 | 13,775,003 | 1,602,000 | 0 | 2,445,312 | ||
| 105 | Jan 4, 2026 06:29 | 4,008 | 20,527,716 | 1,603,000 | 0 | 2,449,408 | ||
| 106 | Jan 4, 2026 06:29 | 4,040 | 15,841,624 | 1,616,000 | 0 | 2,449,408 | ||
| 107 | Jan 4, 2026 06:36 | 4,048 | 17,155,250 | 0 | 1,619,000 | 2,449,408 | ||
| 108 | Jan 4, 2026 06:38 | 4,050 | 18,798,433 | 0 | 1,620,000 | 2,445,312 | ||
| 109 | Jan 4, 2026 06:35 | 4,073 | 17,505,239 | 1,629,000 | 0 | 2,449,408 | ||
| 110 | Jan 17, 2026 17:25 | 4,073 | 16,535,206 | 1,629,000 | 0 | 2,445,312 | ||
| 111 | Jan 5, 2026 06:03 | 4,160 | 16,012,152 | 1,664,000 | 0 | 2,449,408 | ||
| 112 | Jan 18, 2026 01:16 | 4,313 | 21,400,165 | 1,725,000 | 0 | 2,445,312 | ||
| 113 | Jan 5, 2026 06:03 | 4,543 | 16,766,416 | 1,817,000 | 0 | 2,445,312 | ||
| 114 | Jan 5, 2026 06:03 | 4,640 | 23,815,904 | 1,856,000 | 0 | 2,449,408 |