Merge Sort in Objective-C

Merge Sort in

Objective-C

Welcome to the Merge Sort in Objective-C page! Here, you'll find the source code for this program as well as a description of how the program works.

Current Solution

#import <Foundation/Foundation.h>

@interface NSString (Parsing)
- (nullable NSArray<NSNumber*>*)strictIntegerList;
@end

@implementation NSString (Parsing)

- (NSArray<NSNumber*>*)strictIntegerList {
    NSArray<NSString*>* parts = [self componentsSeparatedByString:@","];
    NSMutableArray<NSNumber*>* results =
        [NSMutableArray arrayWithCapacity:parts.count];
    NSCharacterSet* invertedDigits =
        NSCharacterSet.decimalDigitCharacterSet.invertedSet;

    for (NSString* raw in parts) {
        NSString* s = [raw stringByTrimmingCharactersInSet:
                               NSCharacterSet.whitespaceAndNewlineCharacterSet];
        if (s.length == 0) return nil;

        NSString* core = ([s hasPrefix:@"-"] || [s hasPrefix:@"+"])
                             ? [s substringFromIndex:1]
                             : s;
        if (core.length == 0 ||
            [core rangeOfCharacterFromSet:invertedDigits].location !=
                NSNotFound)
            return nil;

        [results addObject:@(s.longLongValue)];
    }
    return (results.count >= 2) ? results : nil;
}

@end

@interface NSArray (Sorting)
- (NSArray<NSNumber*>*)sortedArrayUsingMergeSort;
@end

@interface NSArray (SortingInternal)
- (NSArray<NSNumber*>*)recursivelySortedArray;
- (NSArray<NSNumber*>*)mergedWithArray:(NSArray<NSNumber*>*)other;
@end

@implementation NSArray (Sorting)

- (NSArray<NSNumber*>*)sortedArrayUsingMergeSort {
    if (self.count < 2) return self;
    return [self recursivelySortedArray];
}

@end

@implementation NSArray (SortingInternal)

- (NSArray<NSNumber*>*)recursivelySortedArray {
    if (self.count < 2) return self;

    NSUInteger mid = self.count / 2;

    NSArray* left =
        [[self subarrayWithRange:NSMakeRange(0, mid)] recursivelySortedArray];

    NSArray* right =
        [[self subarrayWithRange:NSMakeRange(mid, self.count - mid)]
            recursivelySortedArray];

    return [left mergedWithArray:right];
}

- (NSArray<NSNumber*>*)mergedWithArray:(NSArray<NSNumber*>*)other {
    NSMutableArray* result =
        [NSMutableArray arrayWithCapacity:self.count + other.count];

    NSUInteger i = 0, j = 0;

    while (i < self.count && j < other.count) {
        if ([self[i] compare:other[j]] != NSOrderedDescending) {
            [result addObject:self[i++]];
        } else {
            [result addObject:other[j++]];
        }
    }

    if (i < self.count) {
        [result addObjectsFromArray:[self subarrayWithRange:NSMakeRange(
                                                                i, self.count -
                                                                       i)]];
    }

    if (j < other.count) {
        [result
            addObjectsFromArray:[other
                                    subarrayWithRange:NSMakeRange(
                                                          j, other.count - j)]];
    }

    return result;
}

@end

int main(int argc, const char* argv[]) {
    @autoreleasepool {
        const char* usage =
            "Usage: please provide a list of at least two integers to sort in "
            "the format \"1, 2, 3, 4, 5\"";

        if (argc < 2) {
            puts(usage);
            return 1;
        }

        NSArray<NSNumber*>* numbers = @(argv[1]).strictIntegerList;

        if (!numbers) {
            puts(usage);
            return 1;
        }

        NSString* output = [[numbers sortedArrayUsingMergeSort]
            componentsJoinedByString:@", "];

        puts(output.UTF8String);
    }
    return 0;
}

Merge Sort in Objective-C was written by:

• Harshal Singh Raushan
• rzuckerm
• Ștefan-Iulian Alecu

If you see anything you'd like to change or update, please consider contributing.

How to Implement the Solution

No 'How to Implement the Solution' section available. Please consider contributing.

How to Run the Solution

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