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 #ifdefs 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

5% 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.

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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The 299 solved problems (that's level 11) had an average difficulty of 32.4% at Project Euler and
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.

more about me can be found on my homepage, especially in my coding blog.
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