# 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.).

# 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
154 - Exploring Pascal's pyramid 16.53 seconds
211 - Divisor Square Sum 14.64 seconds
229 - Four Representations using Squares 10.46 seconds
103 - Special subset sums: optimum 4.27 seconds
148 - Exploring Pascal's triangle 3.53 seconds
146 - Investigating a Prime Pattern 3.21 seconds
214 - Totient Chains 2.69 seconds
127 - abc-hits 2.41 seconds
357 - Prime generating integers 1.96 seconds
60 - Prime pair sets 1.69 seconds

Note: 147 out of 206 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
165 - Intersections 68.9 MB
303 - Multiples with small digits 46.2 MB
193 - Squarefree Numbers 39.1 MB
266 - Pseudo Square Root 36.3 MB
75 - Singular integer right triangles 26.3 MB
179 - Consecutive positive divisors 21.6 MB
39 - Integer right triangles 21.3 MB
87 - Prime power triples 20.1 MB
113 - Non-bouncy numbers 18.4 MB

Note: 148 out of 206 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
211 - Divisor Square Sum 262.5
291 - Panaitopol Primes 255.8
259 - Reachable Numbers 209.3
154 - Exploring Pascal's pyramid 99.2
165 - Intersections 42.0
229 - Four Representations using Squares 39.0
193 - Squarefree Numbers 29.3
303 - Multiples with small digits 27.7
266 - Pseudo Square Root 25.7
357 - Prime generating integers 22.1

# 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.

problem lines of code comments blank lines
80 - Square root digital expansion 234 66 42
60 - Prime pair sets 204 65 38
54 - Poker hands 188 28 26
146 - Investigating a Prime Pattern 187 59 41
98 - Anagramic squares 169 49 42
50 - Consecutive prime sum 168 46 38
119 - Digit power sum 159 34 27
291 - Panaitopol Primes 154 51 40
130 - Composites with prime repunit property 145 58 38
90 - Cube digit pairs 141 32 28

Note: 98 out of 206 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.

5% 63 31% 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 (and 53 more)
10% 7 3% 54, 69, 71, 76, 81, 99, 357
15% 14 7% 51, 62, 65, 73, 74, 85, 93, 102, 112, 205 (and 4 more)
20% 11 5% 60, 61, 64, 70, 72, 80, 82, 87, 89, 145 (and 1 more)
25% 14 7% 66, 68, 75, 77, 83, 91, 96, 104, 120, 124 (and 4 more)
30% 10 5% 78, 95, 100, 108, 113, 116, 119, 123, 173, 204
35% 17 8% 84, 86, 94, 98, 101, 107, 114, 115, 117, 121 (and 7 more)
40% 10 5% 88, 90, 122, 131, 174, 207, 214, 231, 235, 265
45% 20 10% 103, 105, 109, 111, 118, 129, 130, 132, 134, 135 (and 10 more)
50% 15 7% 127, 133, 139, 144, 146, 148, 149, 166, 169, 190 (and 5 more)
55% 8 4% 128, 150, 158, 172, 178, 185, 193, 250
60% 7 3% 154, 159, 160, 186, 213, 240, 249
65% 3 1% 165, 201, 266
70% 7 3% 161, 163, 170, 171, 181, 229, 259
75% - -
80% - -
85% - -
90% - -
95% - -
100% - -
206 27.5%

# Heatmap

green problems solve the original Project Euler problem and have a perfect score of 100% at Hackerrank, too.
yellow problems score less than 100% at Hackerrank (but still solve the original problem).
gray problems are already solved but I haven't published my solution yet.
blue problems are solved and there wasn't a Hackerrank version of it at the time I solved it or I didn't care about it because it differed too much.
red problems are solved but exceed the time limit of one minute.

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

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 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
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 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
The 206 solved problems had an average difficulty of 27.5% at Project Euler and
I scored 12,626 points (out of 14300 possible points, top rank was 20 out ouf ≈60000 in July 2017) at Hackerrank's Project Euler+.
Look at my progress and performance pages to get more details.

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

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.
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