Project Euler 28

28.cpp

#include <iostream>

using namespace::std;

//  Calculates the sum of the diagonals of number spiral size s x s.
int spiralDiagonalSum(int s) {
    // The size of the spiral
    int start = s*s;
    // Starting array offset
    int offset = s-1;
    int answer = 0;
    while (offset > 0) {
        // Sum each of 4 "corners"
        for (int i = 0; i < 4; i++){
            answer += start;
            // Move to the next corner
            start -= offset;
        }
        // Move one row in / one column in
        offset -= 2;
    }
    // Sum of all corners + 1 (the center of the spiral)
    return answer + 1;
}

int  main(void) {
    // SHOW ME THAT SUM YEAAAAAAAH
    cout << spiralDiagonalSum(1001);
}