Yandex - Alrorithm.cs

//user1 [(8, 12), (17, 22)]
//user2 [(5, 11), (14, 18), (20, 23), (42, 55)]
//=> [(8, 11), (17, 18), (20, 22)]


//user1 [(8, 15), (17, 22)]
//user2 [(5, 11), (14, 18), (20, 23), (42, 55)]
//=> [(8, 11), (14, 15), (17, 18), (20, 22)]

//user1 [(8, 10), (13, 15)]
//user2 [(11, 12), (16, 18)]
//=> []

//user1 [(8, 20), (21, 25)]
//user2 [(11, 12), (16, 18)]
//=>  [(11,12),(16,18)]

private static (int start, int end)? GetIntersec((int start, int end) first, (int start, int end) second)
{
    if (first.end < second.first || second.end < first.start)
    {
        return null;
    }
    return (Math.Max(first.start, second.start), Math.Min(first.end, second.end));
}

private static List<(int start, int end)> IntersecIntervals((int start, int end)[] user1, (int start, int end)[] user2)
{
    var intervals = new List<(int start, int end)>();

    var first = 0;
    var second = 0;

    while (first < user1.Length && second < user2.Length)
    {
        var interval = GetIntersec(user1[first], user2[second]);

        if (interval != null)
        {
            intervals.Add(interval);
        }

        var edge = Max.Min(user1[first].end, user2[second].end);

        if (user1[first].end == edge)
        {
            first++;
        }

        if (user2[second].end == edge)
        {
            second++;
        }
    }

    return intervals;
}