比较两个字符串 找出相同区域

- (NSArray *)matchLongestSubstrings:(NSString *)str1 with:(NSString *)str2
{
    //    所有重复的字符串
    NSArray<NSString *> *matchingStrArr = [NSArray array];
    for (NSUInteger i = 0; i < str1.length; i++) {
        unichar c = [str1 characterAtIndex:i];
        NSString *s = [NSString stringWithFormat:@"%C", c];

        matchingStrArr = [matchingStrArr arrayByAddingObjectsFromArray:[self compareStr1:str1 toStr2:str2 withCharacterString:s indexInStr1:i]];
    }

    // 去掉重复的数据
    NSSet<NSString *> *matchingStrSet = [NSSet setWithArray:matchingStrArr];
    matchingStrArr = [matchingStrSet allObjects];

    // 数组内字符串按length降序排列
    matchingStrArr = [matchingStrArr sortedArrayUsingComparator:^NSComparisonResult(id _Nonnull obj1, id _Nonnull obj2) {
        return ((NSString *)obj1).length < ((NSString *)obj2).length;
    }];

    NSInteger longestLength = matchingStrArr.firstObject.length;
    __block NSArray *longestStrArr = [NSArray array];
    [matchingStrArr enumerateObjectsUsingBlock:^(NSString *_Nonnull obj, NSUInteger idx, BOOL *_Nonnull stop) {
        if (obj.length == longestLength) {
            longestStrArr = [longestStrArr arrayByAddingObject:obj];
        } else {
            *stop = YES;
        }
    }];

    return longestStrArr;
}
- (NSArray *)compareStr1:(NSString *)str1 toStr2:(NSString *)str2 withCharacterString:(NSString *)s indexInStr1:(NSUInteger)i
{
    if (![str2 containsString:s]) {
        return nil;
    }

    NSRange rangeOfStr2 = [str2 rangeOfString:s];

    NSMutableArray *longestStrArr = [NSMutableArray array];
    for (NSUInteger j = rangeOfStr2.location, ii = i; j < str2.length && ii < str1.length; j++, ii++) {
        if ([[str1 substringWithRange:NSMakeRange(ii, 1)] isEqualToString:[str2 substringWithRange:NSMakeRange(j, 1)]]) {
            if (j == str2.length - 1 || ii == str1.length - 1) { //匹配到字符串最后一个字符
                NSString *sameStr = [str1 substringWithRange:NSMakeRange(i, ii + 1 - i)];
                [longestStrArr addObject:sameStr];
            }
        } else {
            NSString *sameStr = [str1 substringWithRange:NSMakeRange(i, ii - i)];
            [longestStrArr addObject:sameStr];
            break;
        }
    }

    if (str2.length <= 1) {
        return nil; // str2只剩1个字符，结束递归调用
    }

    str2 = [str2 substringFromIndex:1];
    if (str2.length > 1) {
        [longestStrArr addObjectsFromArray:[self compareStr1:str1 toStr2:str2 withCharacterString:s indexInStr1:i]];
    }

    return longestStrArr;
}