按父親兒童排序數組

Question

我有一個自定義對象數組。這些對象表示二進制文件中的段。 屬性loc在文件中保存對象自己的位置，其中prev保存「上一個」對象的位置。在此情況下，「上一個」和「下一個」並不一定意味着該對象在文件中彼此相繼出現。 第一個對象有prev = 0。最後一個對象沒有後續對象，其位置保持爲prev。

我該如何實現這樣的排序？最初不知道對象的數量。

//My custom object 
@interface MyObject : NSObject 

@property (nonatomic, assign) NSInteger loc, prev; 

@end 

//In the implementation of some other class 
NSMutableArray *array = [NSMutableArray new]; 

{// order should be 6 
    MyObject *obj = [MyObject new]; 
    obj.loc = 3000; 
    obj.prev = 111; 
    [array addObject:obj]; 
} 
{// order should be 2 
    MyObject *obj = [MyObject new]; 
    obj.loc = 2000; 
    obj.prev = 222; 
    [array addObject:obj]; 
} 
{// order should be 4 
    MyObject *obj = [MyObject new]; 
    obj.loc = 333; 
    obj.prev = 4000; 
    [array addObject:obj]; 
} 
{// order should be 1 
    MyObject *obj = [MyObject new]; 
    obj.loc = 222; 
    obj.prev = 5000; 
    [array addObject:obj]; 
} 
{// order should be 5 
    MyObject *obj = [MyObject new]; 
    obj.loc = 111; 
    obj.prev = 333; 
    [array addObject:obj]; 
} 
{// order should be 3 
    MyObject *obj = [MyObject new]; 
    obj.loc = 4000; 
    obj.prev = 2000; 
    [array addObject:obj]; 
} 
{// order should be 0 
    MyObject *obj = [MyObject new]; 
    obj.loc = 5000; 
    obj.prev = 0; 
    [array addObject:obj]; 
} 

Answer 1

嘗試使用辭書排序：

NSArray *sorted = [array sortedArayUsingComparator:^(id obj1, id obj2) { 
    if ([obj1 parentID] < [obj2 parentID] { 
     return NSOrderedAscending; 
    } else if ([obj1 parentID] > [obj2 parentID] { 
     return NSOrderedDescending; 
    } else if ([obj1 ID] < [obj2 ID] { 
     return NSOrderedAscending; 
    } else if ([obj1 ID] > [obj2 ID] { 
     return NSOrderedDescending; 
    } else { 
     return NSOrderedSame; 
    } 
}]; 

Answer 2

沒關係，我知道了。

NSMutableArray *unordered = [[NSMutableArray alloc] initWithArray:array]; 
NSMutableArray *ordered = [NSMutableArray new]; 

for(MyObject *myObj in array) 
{ 
    if(!myObj.prev) 
    { 
     [orderedTables addObject:myObj]; 
     [unorderedTables removeObject:myObj]; 
     break; 
    } 
} 

int counter = 0; 
while(unordered.count && counter < ordered.count) 
{ 
    MyObject *obj1 = [ordered objectAtIndex:counter++]; 

    for(int i = 0; i < unordered.count; ++i) 
    { 
     MyObj *obj2 = [unordered objectAtIndex:i]; 

     if(obj2.prev == obj1.loc) 
     { 
      [ordered addObject:obj2]; 
      [unordered removeObject:obj2]; 
      break; 
     } 
    } 
}