Test System

Most of my development is done on a Intel® Core™ i7-2600K CPU @ 3.40GHz.
My default compiler is G++ with a x86_64 target and its command-line settings are
g++ -O3 -march=native -fno-exceptions -fno-rtti -std=c++11

All solutions are single-threaded and run on the CPU only (no GPU etc.).

You'll find below the following Top Ten lists:

In addition a summary of the difficulty is presented.

Execution Time

The majority of my C++ solutions need much longer to compile than to run.
The "slowest" solutions are (user time displayed by time):

problem seconds
501 - Eight Divisors 56.33 seconds
407 - Idempotents 47.22 seconds
549 - Divisibility of factorials 26.77 seconds
141 - Investigating progressive numbers, n, which are ... 21.33 seconds
154 - Exploring Pascal's pyramid 16.53 seconds
211 - Divisor Square Sum 14.64 seconds
229 - Four Representations using Squares 10.46 seconds
571 - Super Pandigital Numbers 8.88 seconds
348 - Sum of a square and a cube 5.59 seconds
103 - Special subset sums: optimum 4.27 seconds

Note: 177 out of 270 solutions find the correct result in less than 0.1 seconds.

It's not an "officially enforced" limit but each Project Euler problem should be solvable in less than one minute.
I needed much longer to find the correct solutions for these problems:

problem seconds factor
291 - Panaitopol Primes 112 seconds 1.87x

Memory Consumption

The GCC standard library consumes about 2 MByte RAM (basic I/O, etc.).
According to Project Euler, the problems are designed such that a smart solution needs no more than 256 MByte.

problem peak memory consumption
259 - Reachable Numbers 138.6 MB
341 - Golomb's self-describing sequence 133.3 MB
425 - Prime connection 113.6 MB
155 - Counting Capacitor Circuits 105.7 MB
165 - Intersections 68.9 MB
309 - Integer Ladders 59.2 MB
303 - Multiples with small digits 46.2 MB
222 - Sphere Packing 45.2 MB
407 - Idempotents 41.2 MB
549 - Divisibility of factorials 41.2 MB

Note: 181 out of 270 solutions allocate less than 2.5 MByte.

Some solutions could be modified to use smaller data types, especially because an int is 8 bytes on my system (64 bit compiler).
The size of the compiled binary is never an issue regarding memory consumption because all are way below 100 kByte (vast majority only about 10 kByte).

"Expensive" Solutions

These solutions require both lots of CPU time and tons of memory.
(I multiply execution time in seconds by memory consumption in MByte to get my "factor")

problem factor
407 - Idempotents 1,947.2
549 - Divisibility of factorials 1,103.2
501 - Eight Divisors 822.4
211 - Divisor Square Sum 262.5
291 - Panaitopol Primes 255.8
155 - Counting Capacitor Circuits 220.9
259 - Reachable Numbers 209.3
425 - Prime connection 188.5
222 - Sphere Packing 101.2
154 - Exploring Pascal's pyramid 99.2

"Lopsided" Solutions

These solutions require lots of CPU time or tons of memory - but not both.
Usually there is a trade-off between CPU time and memory consumption and most likely I didn't find a proper balance for these problems.
My standard approach is to prefer faster code and accept higher memory usage - as long as it's below 256 MByte.

I divide execution time in seconds by memory consumption in MByte to get my "imbalance", if it's smaller than one then I take it's inverse.

problem imbalance seconds peak memory consumption
291 - Panaitopol Primes 7,479 112 seconds 2.3
341 - Golomb's self-describing sequence 1,139 0.11 seconds 133.3
141 - Investigating progressive numbers, n, which are ... 928 21.33 seconds 2.3
113 - Non-bouncy numbers 645 0.02 seconds 18.4
  72 - Counting fractions 320 0.03 seconds 13.5
571 - Super Pandigital Numbers 287 8.88 seconds 2.3
148 - Exploring Pascal's triangle 236 3.53 seconds 2.3
103 - Special subset sums: optimum 225 4.27 seconds 2.3
149 - Searching for a maximum-sum subsequence 204 0.07 seconds 17.6
510 - Tangent Circles 182 4.17 seconds 2.3
Note: to compensate for timing inaccuracies I added 0.005 seconds to each execution time when computing the imbalance.
Moreover, the memory overhead of the C++ runtime is estimated to be 2.26 MByte and subtracted from peak memory usage.

Code Metrics

C++ programs tend to be a bit longer than other popular languages (such as Python).
The metric "lines of code" excludes comments, empty lines and preprocessor commands.

About half of the program in the Top Ten are related to primes numbers. My Miller-Rabin primality test needs about 150 lines.
In general, most of the "bigger" solution contain a substantial amount of code that I just copy from my toolbox.
The actual amount of original code is therefore substantially lower.

problem lines of code comments blank lines
304 - Primonacci 236 77 63
  80 - Square root digital expansion 234 66 42
152 - Writing 1/2 as a sum of inverse squares 209 74 44
  60 - Prime pair sets 206 65 38
146 - Investigating a Prime Pattern 190 60 42
  54 - Poker hands 188 28 26
126 - Cuboid layers 187 57 40
280 - Ant and seeds 179 56 46
313 - Sliding game 170 60 33
  98 - Anagramic squares 169 49 42

Note: 108 out of 270 solutions have less than 50 lines of code.

Difficulty

Each problem has a "rating" at Project Euler. Very easy have a rating of 5%, while the highest is 100%.
The right column shows how many of my solved problems fall into that category.

rating solved problems links
5% 63 23.3% 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 (and 48 more)
10% 9 3.3% 54, 69, 71, 76, 81, 99, 357, 387, 549
15% 18 6.7% 51, 62, 65, 73, 74, 85, 93, 102, 112, 205, 301, 345, 346, 347, 381 (and 3 more)
20% 17 6.3% 60, 61, 64, 70, 72, 80, 82, 87, 89, 145, 187, 315, 323, 407, 429 (and 2 more)
25% 21 7.8% 66, 68, 75, 77, 83, 91, 96, 104, 120, 124, 125, 179, 203, 293, 329 (and 6 more)
30% 14 5.2% 78, 95, 100, 108, 113, 116, 119, 123, 173, 204, 313, 321, 371, 510
35% 22 8.1% 84, 86, 94, 98, 101, 107, 114, 115, 117, 121, 151, 188, 243, 277, 297 (and 7 more)
40% 13 4.8% 88, 90, 110, 122, 131, 174, 207, 214, 231, 235, 265, 287, 501
45% 21 7.8% 103, 105, 109, 111, 118, 129, 130, 132, 134, 135, 136, 138, 142, 162, 164 (and 6 more)
50% 21 7.8% 106, 127, 133, 137, 139, 144, 146, 148, 149, 166, 169, 190, 211, 215, 230 (and 6 more)
55% 11 4.1% 126, 128, 150, 158, 172, 178, 185, 193, 218, 250, 306
60% 13 4.8% 141, 154, 155, 159, 160, 182, 186, 209, 213, 222, 240, 249, 523
65% 15 5.6% 147, 152, 165, 168, 196, 200, 201, 226, 227, 232, 239, 247, 266, 274, 280
70% 12 4.4% 161, 163, 170, 171, 181, 189, 199, 219, 229, 259, 260, 273
75% - -
80% - -
85% - -
90% - -
95% - -
100% - -
270 31.3%

Heatmap

Please click on a problem's number to open my solution to that problem:

green   solutions solve the original Project Euler problem and have a perfect score of 100% at Hackerrank, too
yellow solutions score less than 100% at Hackerrank (but still solve the original problem easily)
gray problems are already solved but I haven't published my solution yet
blue solutions are relevant for Project Euler only: there wasn't a Hackerrank version of it (at the time I solved it) or it differed too much
orange problems are solved but exceed the time limit of one minute or the memory limit of 256 MByte
red problems are not solved yet but I wrote a simulation to approximate the result or verified at least the given example - usually I sketched a few ideas, too

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75
76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100
101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125
126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150
151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175
176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200
201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225
226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250
251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275
276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300
301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325
326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350
351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375
376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400
401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425
426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450
451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475
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501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525
526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550
551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575
The 270 solved problems (level 10) had an average difficulty of 31.3% at Project Euler and
I scored 13,386 points (out of 15600 possible points, top rank was 17 out of ≈60000 in August 2017) at Hackerrank's Project Euler+.

My username at Project Euler is stephanbrumme while it's stbrumme at Hackerrank.

Look at my progress and performance pages to get more details.

more about me can be found on my homepage, especially in my coding blog.
some names mentioned on this site may be trademarks of their respective owners.
thanks to the KaTeX team for their great typesetting library !