<< problem 21 - Amicable numbers | Non-abundant sums - problem 23 >> |
Problem 22: Names scores
(see projecteuler.net/problem=22)
Using names.txt, a 46K text file containing over five-thousand first names, begin by sorting it into alphabetical order.
Then working out the alphabetical value for each name, multiply this value by its alphabetical position in the list to obtain a name score.
For example, when the list is sorted into alphabetical order, COLIN, which is worth 3 + 15 + 12 + 9 + 14 = 53, is the 938th name in the list.
So, COLIN would obtain a score of 938 x 53 = 49714.
What is the total of all the name scores in the file?
My Algorithm
When using an std::set
all its elements are automatically sorted.
A second container, my std::map
named sorted
contains each name as a key and its position in that set.
All names are written in uppercase - and my program doesn't verify it.
The value of a name is defined as the sum of its letters where A=1, B=2, ... which boils down to value += c - 'A' + 1
Modifications by HackerRank
The modified Hackerrank differs significantly and is surprisingly easier than the original problem.
Note
Project Euler's file can be easily parsed in C++.
Initially I included it in my source code (which works flawlessly) but then decided to read from STDIN.
Interactive test
This feature is not available for the current problem.
My code
… was written in C++11 and can be compiled with G++, Clang++, Visual C++. You can download it, as well as the input data, too.
The code contains #ifdef
s to switch between the original problem and the Hackerrank version.
Enable #ifdef ORIGINAL
to produce the result for the original problem (default setting for most problems).
#include <iostream>
#include <string>
#include <map>
#include <set>
//#define ORIGINAL
// read a single name from STDIN, syntax: "abc","def","xyz"
std::string readName()
{
std::string result;
while (true)
{
// read one character
char c = std::cin.get();
// no more input ?
if (!std::cin)
break;
// ignore quotes
if (c == '"')
continue;
// finish when a comma appears
if (c == ',')
break;
// nope, just an ordinary letter (no further checks whether c in 'A'..'Z')
result += c;
}
return result;
}
int main()
{
// note: an std::set is always sorted
std::set<std::string> names;
#ifdef ORIGINAL
while (true)
{
// read a single name, abort when empty
auto name = readName();
if (name.empty())
break;
names.insert(name);
}
#else
unsigned int numNames;
std::cin >> numNames;
while (numNames--)
{
// Hackerrank's names are separated by a space
std::string name;
std::cin >> name;
// add to our set
names.insert(name);
}
#endif
// walk through all names in alphabetic order, keep track of their position
// store both information as [name] => [pos]
std::map<std::string, unsigned int> sorted;
unsigned int pos = 1;
for (auto name : names)
sorted[name] = pos++;
#ifdef ORIGINAL
// original problem
unsigned int sum = 0;
for (auto name : sorted)
{
unsigned int value = 0;
// 'A' = 1, 'B' = 2, ..., 'Z' = 26
for (auto c : name.first)
value += c - 'A' + 1;
// multiply by position
sum += value * name.second;
}
std::cout << sum << std::endl;
#else
unsigned int queries;
std::cin >> queries;
while (queries--)
{
std::string name;
std::cin >> name;
unsigned int value = 0;
// 'A' = 1, 'B' = 2, ..., 'Z' = 26
for (auto c : name)
value += c - 'A' + 1;
// multiply by position
value *= sorted[name];
std::cout << value << std::endl;
}
#endif
return 0;
}
This solution contains 16 empty lines, 18 comments and 10 preprocessor commands.
Benchmark
The correct solution to the original Project Euler problem was found in 0.01 seconds on an Intel® Core™ i7-2600K CPU @ 3.40GHz.
Peak memory usage was about 3 MByte.
(compiled for x86_64 / Linux, GCC flags: -O3 -march=native -fno-exceptions -fno-rtti -std=gnu++11 -DORIGINAL
)
See here for a comparison of all solutions.
Note: interactive tests run on a weaker (=slower) computer. Some interactive tests are compiled without -DORIGINAL
.
Changelog
February 23, 2017 submitted solution
April 4, 2017 added comments
May 9, 2017 read names from STDIN
Hackerrank
see https://www.hackerrank.com/contests/projecteuler/challenges/euler022
My code solves 2 out of 2 test cases (score: 100%)
Difficulty
Project Euler ranks this problem at 5% (out of 100%).
Hackerrank describes this problem as easy.
Note:
Hackerrank has strict execution time limits (typically 2 seconds for C++ code) and often a much wider input range than the original problem.
In my opinion, Hackerrank's modified problems are usually a lot harder to solve. As a rule thumb: brute-force is rarely an option.
Links
projecteuler.net/thread=22 - the best forum on the subject (note: you have to submit the correct solution first)
Code in various languages:
C# www.mathblog.dk/project-euler-22-what-is-the-total-of-all-the-name-scores-in-the-file-of-first-names/ (written by Kristian Edlund)
C github.com/eagletmt/project-euler-c/blob/master/20-29/problem22.c (written by eagletmt)
Java github.com/nayuki/Project-Euler-solutions/blob/master/java/p022.java (written by Nayuki)
Javascript github.com/dsernst/ProjectEuler/blob/master/22 Names scores.js (written by David Ernst)
Go github.com/frrad/project-euler/blob/master/golang/Problem022.go (written by Frederick Robinson)
Mathematica github.com/nayuki/Project-Euler-solutions/blob/master/mathematica/p022.mathematica (written by Nayuki)
Haskell github.com/nayuki/Project-Euler-solutions/blob/master/haskell/p022.hs (written by Nayuki)
Scala github.com/samskivert/euler-scala/blob/master/Euler022.scala (written by Michael Bayne)
Those links are just an unordered selection of source code I found with a semi-automatic search script on Google/Bing/GitHub/whatever.
You will probably stumble upon better solutions when searching on your own. Maybe not all linked resources produce the correct result and/or exceed time/memory limits.
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 | |
black | problems are solved but access to the solution is blocked for a few days until the next problem is published | |
the flashing problem is the one I solved most recently |
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I scored 13526 points (out of 15700 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.
Copyright
I hope you enjoy my code and learn something - or give me feedback how I can improve my solutions.
All of my solutions can be used for any purpose and I am in no way liable for any damages caused.
You can even remove my name and claim it's yours. But then you shall burn in hell.
The problems and most of the problems' images were created by Project Euler.
Thanks for all their endless effort !!!
<< problem 21 - Amicable numbers | Non-abundant sums - problem 23 >> |