objective-c – 在NSArray中搜索最近的数字

是否有一种简单的方法来搜索NSArray数字,以找到与用户输入数字匹配的最近(或确切存在)匹配？

假设我有一个这样的数组：7,23,4,11,18,2,用户输入5.

程序以接近度的降序返回三个最接近的值：4,7,最重要的是给出三个对象的NSArray索引：2,5.

解决方法

更新：请参阅下面的解决方案,比我的第一个更好.

这是使用NSDictionary包装器为每个数字及其索引提供的解决方案,使用比较器块进行排序.它可能不会很好地扩展,但它可以完成工作.

static Nsstring *const kValueKey = @"value";
static Nsstring *const kIndexKey = @"index";

+ (void)searchArray:(NSArray *)array forClosestValuesTo:(int)value resultValues:(NSArray **)values resultIndexes:(NSArray **)indexes
{
    NSMutableArray *searchObjs = [NSMutableArray arrayWithCapacity:[array count]];

    [array enumerateObjectsUsingBlock:^(id obj,NSUInteger idx,BOOL *stop) {
        [searchObjs addobject:[NSDictionary dictionaryWithObjectsAndKeys:obj,kValueKey,[NSNumber numberWithUnsignedInt:idx],kIndexKey,nil]];
    }];

    [searchObjs sortUsingComparator:^NSComparisonResult(id obj1,id obj2) {
        NSUInteger d1 = ABS([[obj1 objectForKey:kValueKey] intValue] - value);
        NSUInteger d2 = ABS([[obj2 objectForKey:kValueKey] intValue] - value);
        if (d1 == d2) { return NSOrderedSame; }
        if (d1 <  d2) { return NSOrderedAscending; }
        return NSOrderedDescending;
    }];

    NSArray *results = [searchObjs subarrayWithRange:NSMakeRange(0,3)];

    if (values) {
        *values = [results valueForKey:kValueKey];
    }

    if (indexes) {
        *indexes = [results valueForKey:kIndexKey];
    }
}

更新：这是一个更新的解决方案,可以对C数组索引进行排序,从而无需使用NSDictionary包装器

static Nsstring *const kValueKey = @"value";
static Nsstring *const kArrayKey = @"array";

int
CSCompareIndexes(void *data,const void *value1,const void *value2)
{
    NSDictionary *dict = (NSDictionary *)data;

    NSArray *array = [dict objectForKey:kArrayKey];
    int valuetoFind = [[dict objectForKey:kValueKey] intValue];

    int index1 = *(int *)value1;
    int index2 = *(int *)value2;

    NSNumber *num1 = [array objectAtIndex:index1];
    NSNumber *num2 = [array objectAtIndex:index2];

    return ABS([num1 intValue] - valuetoFind) - ABS([num2 intValue] - valuetoFind);
}

void
CSSearchNumberArray(NSArray *array,int valuetoFind,NSArray **resultValues,NSArray **resultIndexes)
{
    NSInteger numValues = [array count];

    NSUInteger *indexes = malloc(sizeof(NSUInteger) * numValues);
    assert(indexes);

    int i;
    for (i = 0; i < numValues; i++) {
        indexes[i] = i;
    }

    NSDictionary *data = [NSDictionary dictionaryWithObjectsAndKeys:array,kArrayKey,[NSNumber numberWithInt:valuetoFind],nil];
    qsort_r(indexes,numValues,sizeof(NSUInteger),(void *)data,CSCompareIndexes);

    NSMutableArray *tmpValues  = [NSMutableArray arrayWithCapacity:3],*tmpIndexes = [NSMutableArray arrayWithCapacity:3];

    for (i = 0; i < 3; i++) {
        [tmpValues addobject:[array objectAtIndex:indexes[i]]];
        [tmpIndexes addobject:[NSNumber numberWithInt:indexes[i]]];
    }

    if (resultValues) {
        *resultValues = [NSArray arrayWithArray:tmpValues];
    }

    if (resultIndexes) {
        *resultIndexes = [NSArray arrayWithArray:tmpIndexes];
    }

    free(indexes);
}

int main (int argc,char *argv[])
{
    NSAutoreleasePool *pool = [NSAutoreleasePool new];

    NSMutableArray *test = [NSMutableArray array];

    int i;
    for (i = 0; i < 10; i++) {
        [test addobject:[NSNumber numberWithInt:(arc4random() % 100)]];
    }

    NSLog(@"Searching: %@",test);

    NSArray *values,*indexes;
    CSSearchNumberArray(test,50,&values,&indexes);

    NSLog(@"Values: %@",values);
    NSLog(@"Indexes: %@",indexes);

    [pool drain];
    return 0;
}

原文地址：https://www.jb51.cc/c/110601.html