40 lines
1000 B
Objective-C
40 lines
1000 B
Objective-C
//
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// Shuffle.m
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// Cog
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//
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// Created by Vincent Spader on 1/14/06.
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// Revised by Eric Hanneken on 2/14/08.
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// Copyright 2008 Vincent Spader. All rights reserved.
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//
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#import "Shuffle.h"
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#import "NSArray+ShuffleUtils.h"
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@implementation Shuffle
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+ (void)initialize {
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static BOOL initialized = NO;
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if(!initialized) {
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// Call srandom() exactly once.
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srandom((unsigned)time(NULL));
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initialized = YES;
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}
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}
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+ (NSMutableArray*)shuffleList:(NSArray*)l {
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NSArray* randomLongs = [NSArray arrayWithRandomLongs:[l count]];
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// randomLongs is an array of random integers, equal in length to l.
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NSArray* pairs = [NSArray zipArray:randomLongs withArray:l];
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// randomLongs and l are paired.
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NSArray* shuffledPairs = [pairs sortedArrayUsingSelector:@selector(compareFirsts:)];
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// The numbers from randomLongs are sorted in ascending order; the tracks from l
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// are in random order.
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// Peel the tracks off and return them.
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return [[NSArray unzipArray:shuffledPairs] objectAtIndex:1];
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}
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@end
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