TortoiseRacing.js

/**
 Description:

 Two tortoises named A and B must run a race. A starts with an average speed of 720 feet per hour. Young B knows she runs faster than A and furthermore has not finished her cabbage.

 When she starts, at last, she can see that A has a 70 feet lead but B speed is 850 feet per hour. How long will it take B to catch A?

 More generally: given two speeds v1 (A speed, integer > 0) and v2 (B speed, integer > 0) and a lead g (integer > 0) how long will it take B to catch A?

 The result will be an array [h, mn, s] where h, mn, s is the time needed in hours, minutes and seconds (don't worry for fractions of second). If v1 >= v2 then return nil, nothing, null, None or {-1, -1, -1} for C++, C, Go.

 Examples:

 race(720, 850, 70) => [0, 32, 18]
 race(80, 91, 37) => [3, 21, 49]
 */
function race(v1, v2, g) {
    if (v1 >= v2) return null

    let speedDiff = v2-v1
        , hr = Math.floor(g / speedDiff)
        , min = Math.floor((g % speedDiff) * 60 / speedDiff)
        , sec = Math.floor((((g % speedDiff) * 60) % speedDiff) * 60 / speedDiff) // crazy stuff!

    return [hr, min, sec]
}