Factorial in Objective-C

Factorial in

Objective-C

Welcome to the Factorial 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)
@property(nonatomic, readonly, nullable) NSNumber* strictIntegerNumber;
@end

@implementation NSString (Parsing)

- (NSNumber*)strictIntegerNumber {
    NSString* trimmed = [self
        stringByTrimmingCharactersInSet:NSCharacterSet
                                            .whitespaceAndNewlineCharacterSet];
    if (trimmed.length == 0) return nil;

    NSInteger offset = 0;
    if ([trimmed hasPrefix:@"-"] || [trimmed hasPrefix:@"+"]) {
        offset = 1;
    }

    if (trimmed.length <= offset) return nil;

    NSString* core = [trimmed substringFromIndex:offset];
    NSRange invalidRange =
        [core rangeOfCharacterFromSet:NSCharacterSet.decimalDigitCharacterSet
                                          .invertedSet];

    if (invalidRange.location != NSNotFound) {
        return nil;
    }

    return @(trimmed.longLongValue);
}

@end

static unsigned long long Factorial(NSUInteger n) {
    if (n == 0 || n == 1) return 1;

    unsigned long long result = 1;
    for (NSUInteger i = 2; i <= n; i++) {
        result *= i;
    }

    return result;
}

int main(int argc, const char* argv[]) {
    @autoreleasepool {
        const char* usage = "Usage: please input a non-negative integer";
        if (argc < 2) {
            puts(usage);
            return 1;
        }

        NSNumber* number = @(argv[1]).strictIntegerNumber;

        if (!number || number.integerValue < 0) {
            puts(usage);
            return 1;
        }

        printf("%llu\n", Factorial(number.unsignedIntegerValue));
    }
    return 0;
}

Factorial in Objective-C was written by:

• niftycode
• 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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