// // Shuffle.m // Cog // // Created by Vincent Spader on 1/14/06. // Copyright 2006 Vincent Spader. All rights reserved. // #import "Shuffle.h" @implementation Shuffle int sum(int n) { return (n*n+n)/2; } int reverse_sum(int n) { return (int)(ceil((-1.0 + sqrt(1.0 + 8.0*n))/2.0)); } int randint(int low, int high) { return (random()%high)+low; } + (NSMutableArray *)shuffleList:(NSArray *)l { NSMutableArray *a = [l mutableCopy]; NSMutableArray *b = [[NSMutableArray alloc] init]; while([a count] > 0) { int t, r, p; t = sum([a count]); r = randint(1, t); p = reverse_sum(r) - 1; printf("%i, %i, %i, %i\n", [a count], t, r, p); [b insertObject:[a objectAtIndex:p] atIndex:0]; [a removeObjectAtIndex:p]; } [a release]; return [b autorelease]; } @end