Modern western square dance of "patter calls" and "singing calls", the two types of square dance calls. The logos shown on the right are the international square dance logo and the modern Alliance of Round, Traditional and Square-Dance logo. Modern western square dancing is a non-competitive activity. There are no dance competitions, and apart from fun events, no prizes are ever offered or sought for 'best dancer' or 'best square'. Particularly at the 'challenge' levels there is large degree of personal satisfaction to be gained from the problem solving element of completing a dance. At all levels the main elements are to enjoy the
Activity selection problem that |S'| > |S| in the case that multiple maximal solutions have equal sizes. The activity selection problem is notable in that using a greedy algorithm to find a solution will always result in an optimal solution. A pseudocode sketch of the iterative version of the algorithm and a proof of the optimality of its result are included below. Line 1: This algorithm is called "Greedy-Iterative-Activity-Selector", because it is first of all a greedy algorithm, and then it is iterative. There's also a recursive version of this greedy algorithm. Note that these arrays are indexed starting from 1 up to