crab_align_2.cc

#include <iostream>
#include <string>
#include <algorithm>
#include <sstream>
#include <vector>
#include <valarray>
#include <map>
#include <cmath>

using namespace std;

int main() {
    string line;
    getline(cin, line);
    transform(line.begin(), line.end(), line.begin(), [](char ch) {return ch == ',' ? ' ' : ch;});
    istringstream ss(line);
    vector<int> crab_hpos;
    copy(istream_iterator<int>(ss), istream_iterator<int>(), back_inserter(crab_hpos));

    valarray<int> orig(&crab_hpos[0], crab_hpos.size());
    int c_begin = orig.min(), c_end = orig.max();
    map<int, int> ranked;
    // It's the triangle number, now.  For diff of 4, it's 10.
    for (int p = c_begin; p <= c_end; ++p) {
        int diff = (orig - p).apply(abs).apply([] (int n) {return (n * (n + 1)) / 2;}).sum();
        ranked[diff] = p;
    }
    cout << "Ranked choices:" << endl;
    for (auto const & rc : ranked) {
        cout << rc.first << ": " << rc.second << endl;
    }
    cout
        << "Winning position: " << ranked.begin()->second
        << " using " << ranked.begin()->first << " fuel" << endl;
}