Pattern searching

gistfile1.m

//
//  main.m
//  chrono
//
//  Created by Darshan Katrumane on 2/2/15.
//  Copyright (c) 2015 Darshan Katrumane. All rights reserved.
//

#import <Foundation/Foundation.h>
int main(int argc, const char * argv[]) {
    @autoreleasepool {

        NSFileHandle *inputFile = [NSFileHandle fileHandleWithStandardInput];
        NSMutableString *inputString = [NSMutableString string];
        
        NSString *firstLine;
        NSMutableString *string;
        NSMutableString *pattern;
        NSInteger lineCounter = 1;
        
        do {
            NSData *data = [inputFile availableData];
            if ([data length] == 0) {
                NSLog(@"EOF");
                break;
            }
            NSMutableString *tmp = [[NSMutableString alloc] initWithData:data encoding:NSUTF8StringEncoding];
            [tmp replaceOccurrencesOfString:@"\n" withString:@" " options:0 range:NSMakeRange(0, [tmp length])];
            switch (lineCounter) {
                case 1:
                    firstLine = tmp;
                    break;
                case 2:
                    string = tmp;
                case 3:
                    pattern = tmp;
                default:
                    break;
            }
            if (++lineCounter > 3) {
                break;
            }
        } while ([inputString rangeOfString:@";"].location == NSNotFound);
        
        NSArray *inputDatas = [firstLine componentsSeparatedByString:@" "];
        if ([inputDatas count] < 2) {
            NSLog(@"error in input data");
            return -1;
        }
        [string replaceOccurrencesOfString:@" " withString:@"" options:0 range:NSMakeRange(0, [string length])];
        NSInteger stringLength = [[inputDatas objectAtIndex:0] integerValue];
        if(stringLength != [string length]) {
            NSLog(@"error in input data/string");
            return -1;
        }
        // read data into an array
        NSMutableArray *charactersArray = [[NSMutableArray alloc] initWithCapacity:stringLength];
        for (int i=0; i < stringLength; i++) {
            NSString *ichar  = [NSString stringWithFormat:@"%c", [string characterAtIndex:i]];
            [charactersArray addObject:ichar];
        }
        [pattern replaceOccurrencesOfString:@" " withString:@"" options:0 range:NSMakeRange(0, [pattern length])];
        NSInteger patternLength = [[inputDatas objectAtIndex:1] integerValue];
        if(patternLength != [pattern length]) {
            NSLog(@"error in input data/pattern");
            return -1;
        }
        NSMutableArray *patternsArray = [[NSMutableArray alloc] initWithCapacity:patternLength];
        for (int i=0; i < patternLength; i++) {
            NSString *ichar  = [NSString stringWithFormat:@"%c", [pattern characterAtIndex:i]];
            [patternsArray addObject:ichar];
        }
        // iterate the main string
        // main two pointers one for string, the other for the pattern
        // increment each value, if they match
        NSInteger numberOfPatterns = 0;
        for (int characterMarker =0, patternMarker =0; characterMarker < stringLength; characterMarker++) {
            while (patternMarker <= patternLength-1 && characterMarker < stringLength) {
                if ([[patternsArray objectAtIndex:patternMarker] isEqualToString:[charactersArray objectAtIndex:characterMarker]] || [[patternsArray objectAtIndex:patternMarker] isEqualToString:@"*"]) {
                    if (patternMarker < patternLength-1) {
                        characterMarker++;
                    }else if(patternMarker == patternLength-1) {
                        patternMarker = 0;
                        numberOfPatterns++;
                    }
                    patternMarker++;
                } else {
                    patternMarker = 0;
                    break;
                }
            }
        }
        NSLog(@"%lu", numberOfPatterns);
    }
    return 0;
}