Objective-C中的排列/字谜 - 我遗漏了一些东西

- (void)permute:(NSMutableArray *)nums
         result:(NSMutableArray *)result
         temp:(NSMutableArray *)temp
         start:(int)start {
    if (start == nums.count) {
        [result addObject:[temp mutableCopy]];
    } else {
        for (int i = start; i < nums.count; i++) {
            [temp exchangeObjectAtIndex:start withObjectAtIndex:i];
            [self permute:nums result:result temp:temp start:start+1];
            [temp exchangeObjectAtIndex:start withObjectAtIndex:i];
        }
    }
}

- (NSArray *)permute:(NSArray *)nums {
    NSMutableArray *result = [NSMutableArray array];
    NSMutableArray *temp = [NSMutableArray arrayWithArray:nums];
    [self permute:nums result:result temp:temp start:0];
    return result;
}

- (NSArray *)shuffle:(NSArray *)array {
    NSMutableArray *mutableArray = [NSMutableArray arrayWithArray:array];
    for (int i = mutableArray.count - 1; i >= 1; i--) {
        int j = arc4random_uniform((u_int32_t)(i + 1));
        [mutableArray exchangeObjectAtIndex:i withObjectAtIndex:j];
    }
    return mutableArray;
}

- (NSArray *)generateAnagrams:(NSString *)word {
    NSMutableArray *result = [NSMutableArray array];
    [self generateAnagramsHelper:word result:result current:0];
    return result;
}

- (void)generateAnagramsHelper:(NSString *)word
                         result:(NSMutableArray *)result
                        current:(NSInteger)current {
    if (current == word.length - 1) {
        [result addObject:word];
    } else {
        for (NSInteger i = current; i< word.length; i++) {
            NSMutableString *temp = [word mutableCopy];
            [temp replaceCharactersInRange:NSMakeRange(current, 1) withString:[word substringWithRange:NSMakeRange(i, 1)]];
            [self generateAnagramsHelper:temp result:result current:current+1];
        }
    }
}