NSMutableArray Heap Sort

@interface NSMutableArray (HeapSort)


- (void)heapSortUsingComparator:(NSComparator)comparator;


@end




#import "NSMutableArray+HeapSort.h"


@implementation NSMutableArray (HeapSort)


- (void)heapSortUsingComparator:(NSComparator)comparator
{
    if (!comparator) {
        return;
    }
    
    [self buildHeapUsingComparator:comparator];
    
    NSInteger count = [self count];
    for (NSInteger index = count - 1; index >= 1; index--) {
        //交换堆顶和最后一个元素，即每次将剩余元素中的最大者放到最后面
        [self exchangeObjectAtIndex:index withObjectAtIndex:0];
        
        //重新调整堆顶节点成为大顶
        [self adjustHeapUsingComparator:comparator forIndex:0 needAdjustCount:index];
    }
}


#pragma mark - PrivateMethod




- (void)buildHeapUsingComparator:(NSComparator)comparator
{
    NSInteger count = [self count];
    //非叶节点最大序号值为count/2
    for (NSInteger index = count / 2; index >= 0; index--) {
        [self adjustHeapUsingComparator:comparator forIndex:index needAdjustCount:count];
    }
}


- (void)adjustHeapUsingComparator:(NSComparator)comparator forIndex:(NSInteger)index needAdjustCount:(NSInteger)needAdjustCount
{
    NSInteger leftChildIndex = index * 2 + 1;
    NSInteger rightChildIndex = index * 2 + 2;
    NSInteger maxValueIndex = index;
    
    if ( (leftChildIndex < needAdjustCount) && comparator(self[leftChildIndex], self[maxValueIndex]) == NSOrderedDescending) {
        maxValueIndex = leftChildIndex;
    }
    
    if ( (rightChildIndex < needAdjustCount) && comparator(self[rightChildIndex], self[maxValueIndex]) == NSOrderedDescending) {
        maxValueIndex = rightChildIndex;
    }
    
    if (maxValueIndex != index) {
        [self exchangeObjectAtIndex:index withObjectAtIndex:maxValueIndex];
        
        //避免调整之后以max为父节点的子树不是堆
        [self adjustHeapUsingComparator:comparator forIndex:maxValueIndex needAdjustCount:needAdjustCount];
    }
}


@end




测试代码


@interface Person : NSObject


@property (nonatomic, assign) NSInteger age;


@end


@implementation Person


- (NSString *)description
{
    return [NSString stringWithFormat:@"Person:%p, age:%ld",self, (long)self.age];
}


@end




    
NSMutableArray<Person *> *arr = @[].mutableCopy;
for (NSInteger index = 0; index < 15; index++) {
    Person *person = [[Person alloc] init];
    person.age = arc4random() % 128;
    [arr addObject:person];
}
    
NSLog(@"%@", arr);
[arr heapSortUsingComparator:^NSComparisonResult(Person *  _Nonnull obj1, Person *  _Nonnull obj2) {
    if (obj1.age > obj2.age) {
        return NSOrderedDescending;
    }  else if (obj1.age < obj2.age ) {
        return NSOrderedAscending;
     else {
        return NSOrderedSame;
    }
}];
NSLog(@"sort %@", arr);