Puzzle (8-14) (answer)

[bearophile]

Steven Schveighoffer:
> attempt 2 (little bit of cheating, because I know the answer fits within an 
> int):
...

I have modified your code a little, using a poor's man set to speed up the code:

import std.stdio: putr = writefln;
import std.math: sqrt;

void main() {
    int[][int] pairs;
    int[int] squares;
    for (int i = 1; i < short.max; i++)
        squares[i * i] = 0;

    for (int x = 3; ; x++) {
        for (int i = 1; i * i < x; i++) {
            int y = x - (i * i);
            if ((x + y) in squares) {
                auto arr = y in pairs;
                if (arr !is null) {
                    foreach (z; *arr) {
                        if ((x - z) in squares && (x + z) in squares) {
                            putr(x, " ", y, " ", z);
                            return;
                        }
                    }
                }

                arr = x in pairs;
                if (arr is null) {
                    pairs[x] = new int[0];
                    arr = x in pairs;
                }
                *arr ~= y;
            }
        }
    }
}

On my 2 GHz PC it takes 6.97 s to run. I have another trick to try, we'll see if it works...

Later,
bearophile