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@rayfix
Created Mar 16, 2014
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Groups from NSArray
//
// GroupTests.m
//
// Created by Ray Fix on 3/15/14.
//
#import <XCTest/XCTest.h>
#import "NSArray+Groups.h"
@interface GroupTests : XCTestCase
@end
@implementation GroupTests
- (void)testGroupsOfOneFromPopulationOfThree
{
NSArray* groups = [@[@"A", @"B", @"C"] groupsOfSize:1];
NSArray* answer = @[@[@"A"], @[@"B"], @[@"C"]];
XCTAssertEqualObjects(groups, answer);
}
- (void)testGroupsOfTwoFromPopulationOfThree
{
NSArray* groups = [@[@"A", @"B", @"C"] groupsOfSize:2];
NSArray* answer = @[@[@"A",@"B"],@[@"A",@"C"],@[@"B",@"C"]];
XCTAssertEqualObjects(groups, answer);
}
- (void)testGroupsOfThreeFromPopulationOfThree
{
NSArray* groups = [@[@"A", @"B", @"C"] groupsOfSize:3];
NSArray* answer = @[@[@"A",@"B",@"C"]];
XCTAssertEqualObjects(groups, answer);
}
- (void)testGroupsOfThreeFromFromPopulationOfFive
{
NSArray* groups = [@[@"A", @"B", @"C", @"D", @"E"] groupsOfSize:3];
NSArray* answer = @[@[@"A",@"B",@"C"],
@[@"A",@"B",@"D"],
@[@"A",@"B",@"E"],
@[@"A",@"C",@"D"],
@[@"A",@"C",@"E"],
@[@"A",@"D",@"E"],
@[@"B",@"C",@"D"],
@[@"B",@"C",@"E"],
@[@"B",@"D",@"E"],
@[@"C",@"D",@"E"]];
XCTAssertEqualObjects(groups, answer);
}
@end
//
// NSArray+Groups.m
//
// Created by Ray Fix on 3/15/14.
//
#import "NSArray+Groups.h"
@implementation NSArray (Groups)
- (NSArray *)groupsOfSize:(int)n
{
NSAssert(n > 0 && n <= self.count,
@"Illegal group size n=%d array.count = %ld",n,(long)self.count);
NSMutableArray* answer = [NSMutableArray array];
if (n == 1) {
for (id member in self) {
[answer addObject:@[member]];
}
return answer;
}
for (int index = 0 ; index <= self.count - n; ++index) {
id firstObject = self[index];
NSRange remainingPopulationRange = NSMakeRange(index+1, self.count-index-1);
NSArray* remainingPopulation = [self subarrayWithRange:remainingPopulationRange];
NSArray* groups = [remainingPopulation groupsOfSize:n-1];
for (NSArray* group in groups) {
NSMutableArray* combinedGroup = [@[firstObject] mutableCopy];
[combinedGroup addObjectsFromArray:group];
[answer addObject:combinedGroup];
}
}
return answer;
}
@end
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