There are 8 balls numbered from 0 to 7. Seven of them have the same weight. One is heavier. Your task is to find its number.
Your function findBall will receive single argument - scales object. The scales object contains an internally stored array of 8 elements (indexes 0-7), each having the same value except one, which is greater. It also has a public method named getWeight(left, right) which takes two arrays of indexes and returns -1, 0, or 1 based on the accumulation of the values found at the indexes passed are heavier, equal, or lighter.
getWeight returns:
-1 if left pan is heavier
1 if right pan is heavier
0 if both pans weight the same
Examples of scales.getWeight() usage:
scales.getWeight([3], [7]) returns -1 if ball 3 is heavier than ball 7, 1 if ball 7 is heavier, or 0 i these balls have the same weight.
scales.getWeight([3, 4], [5, 2]) returns -1 if weight of balls 3 and 4 is heavier than weight of balls 5 and 2 etc.
So where's the catch, you may ask. Well - the scales is very old. You can use it only 4 TIMES before the scale breaks.
Too easy? Try higher levels: