快速剪辑-助力度咔智能剪辑提效实践

/*** 字符重复度*/private func similarity(s1: String, s2: String) -> Float {    var simiCount: Float = 0    var string2Array = [String]()    for i in 0..<s2.count {        // 从任意位置开始截取到任意位置，闭区间        let string = subOneString(string: s2, from: i)        string2Array.append(string)    }    for i in 0..<s1.count {        let string1 = subOneString(string: s1, from: i)        if string2Array.contains(string1) {            let index2 = string2Array.firstIndex(of: string1)            string2Array.remove(at: index2!)            simiCount = simiCount + 1        }    }    if simiCount == 0 {        return 0.0    }    let rate: Float = simiCount / Float(max(s1.count, s2.count))    return rate}

/*** 莱文斯坦距离，是编辑距离的一种。指两个字串之间，由一个转成另一个所需的最少编辑操作次数。*/-(CGFloat)levenshteinDistance:(NSString *)s1 compare:(NSString *)s2 {    NSInteger n = s1.length;    NSInteger m = s2.length;    // 有一个字符串为空串    if (n * m == 0) {        return n + m;    }    // DP 数组    int D[n + 1][m + 1];    // 边界状态初始化    for (int i = 0; i < n + 1; i++) {        D[i][0] = i;    }    for (int j = 0; j < m + 1; j++) {        D[0][j] = j;    }    // 计算所有 DP 值    for (int i = 1; i < n + 1; i++) {        for (int j = 1; j < m + 1; j++) {            int left = D[i - 1][j] + 1;            int down = D[i][j - 1] + 1;            int left_down = D[i - 1][j - 1];            NSString *i1 = [s1 substringWithRange:NSMakeRange(i - 1, 1)];            NSString *j1 = [s2 substringWithRange:NSMakeRange(j - 1, 1)];            if ([i1 isEqualToString:j1] == NO) {                left_down += 1;            }            D[i][j] = MIN(left, MIN(down, left_down));        }    }    NSInteger maxLength = MAX(s1.length, s1.length);    CGFloat rate = 1.0 - ((CGFloat) D[n][m] / (CGFloat)maxLength);    returnrate;}

/*** 余弦相似性: 首先将字符串向量化，之后在一个平面空间中求出他们向量之间夹角的余弦值。*/-(CGFloat)cos:(NSString *)s1 compare:(NSString *)s2 {    NSMutableSet *setA = [NSMutableSet new];    for (int i = 0; i < [s1 length]; i++) {        NSString *string = [s1 substringWithRange:NSMakeRange(i, 1)];        [setA addObject:string];    }    NSMutableSet *setB = [NSMutableSet new];    for (int i = 0; i < [s2 length]; i++) {        NSString *string = [s2 substringWithRange:NSMakeRange(i, 1)];        [setB addObject:string];    }    // 统计字频    NSMutableDictionary *dicA = [NSMutableDictionary new];    NSMutableDictionary *dicB = [NSMutableDictionary new];    for (NSString *key in setA) {        NSNumber *value = dicA[key];        if (value == nil) {            value = @(0);        }        NSNumber *newValue = @([value integerValue] + 1);        dicA[key] = newValue;    }    for (NSString *key in setB) {        NSNumber *value = dicB[key];        if (value == nil) {            value = @(0);        }        NSNumber *newValue = @([value integerValue] + 1);        dicB[key] = newValue;    }    // 向量化,求并集    NSMutableSet *unionSet = [setA mutableCopy]; //取并集后    [unionSet unionSet:setB];    NSArray *unionArray = [unionSet allObjects];    NSMutableArray *aVec = [[NSMutableArray alloc] initWithCapacity:unionSet.count];    NSMutableArray *bVec = [[NSMutableArray alloc] initWithCapacity:unionSet.count];    for (NSInteger i = 0; i < unionArray.count; i++) {        [aVec addObject:@(0)];        [bVec addObject:@(0)];    }    for (NSInteger i = 0; i < unionArray.count; i++) {        NSString *object = unionArray[i];
        NSNumber *numA =  dicA[object];        if (numA == nil) {            numA = @(0);        }        NSNumber *numB =  dicB[object];        if (numB == nil) {            numB = @(0);        }        aVec[i] = numA;        bVec[i] = numB;
    }    // 分别计算三个参数    NSInteger p1 = 0;    for (NSInteger i = 0; i < aVec.count; i++) {        p1 += ([aVec[i] integerValue] * [bVec[i] integerValue]);    }    CGFloat p2 = 0.0f;    for (NSNumber *i in aVec) {        p2 +=  ([i integerValue] * [i integerValue]);    }    p2 = (CGFloat)sqrt(p2);
    CGFloat p3 = 0.0f;    for (NSNumber *i in bVec) {        p3 +=  ([i integerValue] * [i integerValue]);    }    p3 = (CGFloat)sqrt(p3);    CGFloat rate = ((CGFloat) p1) / (p2 * p3);    return rate;}