gistfile1.txt

func add(x, y) {
    let p1 = {x: x, y: y}
    
    let points = array();
    for (let i = 0; i < points.length; i++) {
        let p2 = points[i];
        if (p2.x == p1.x && p2.y == p1.y) {
            continue;
        }
        
        let p3 = {x: p1.x - (p2.y - p1.y), y: p1.y + (p2.x - p1.x)};
        let p4 = {x: p2.x - (p2.y - p1.y), y: p2.y + (p2.x - p1.x)};
        let p3alt = {x: p1.x + (p2.y - p1.y), y: p1.y - (p2.x - p1.x)};
        let p4alt = {x: p2.x + (p2.y - p1.y), y: p2.y - (p2.x - p1.x)};
        
        if (contains(p3) && contains(p4) || (contains(p3alt) && contains(p4alt))) {
            return true;
        }
    }
    insert(p1)
    return false;
}

let set = {};

func contains(p) {
    return set[p.x + "," + p.y] !== undefined;
}

func insert(p) {
    set[p.x + "," + p.y] = p;
}

func array() {
    let array = [];
    let keys = set.keys;
    for (let i = 0; i < keys; i++) {
        let key = keys[i];
        array.push(p[key]);
    }
    return array;
}