算法导论中优先队列选定下标元素增加到k疑惑 

 1 #define PARENT(i) (i - 1) / 2
 2 
 3 void HEAP-INCREASE-KEY(int* A,int i,int key)
 4 {
 5   if (key < A[i])
 6   {
 7       printf("new key is small than current key");
 8       return;
 9   }
10   A[i] = key;
11   while (i > 0 && A[PARENT(i)] < A[i])
12   {
13       int temp = A[i];
14       A[i] = A[PARENT(i)];
15       A[PARENT(i)] = temp;
16       i = PARENT(i);
17   }
18   return;         
19 }

但这样真的完全维护了堆的性质了么？

->　 　　A[PARENT(I)] >= A[i]

我觉得并没有，还应在while循环中加一句：

 1   while(i > 0 && A[PARENT(i)] < A[i])
 2   {
 3       int temp = A[i];
 4       A[i] = A[PARENT(i)];
 5       A[PARENT(i)] = temp;
 6     
 7      //加入的一句算法导论前面的用于堆维护的函数
 8       MAX_HEAPIFY(A,i,heap-size);
 9 
10       i = PARENT(i);
11   }

附上MAX_HEAPIFY(int* A,int i)的函数

#define Left(i) 2 * (i + 1) - 1
#define Right(i) 2* (i + 1) 

void MAX_HEAPIFY(int* A,int i,int heap-size)
{
  int L = Left(i);
  int R = Right(i);
  int large;
  
  if (i <= heap-size && A[L] >= A[i])
  {
      large = L;
  }
  else large = i;
  if (i <= heap-size && A[R] >= A[large])
  {
      large = R;
  }

  if (large != i)
  {
      int temp = A[i];
      A[i] = A[large];
      A[large] = temp;
      MAX_HEAPIFY(A,i,heap-size)
  }
  else return;
}

如果你有正确的思路反驳我，希望能在评论区看见你的身影。

 

posted @ 2022-02-09 20:16  SkySource  阅读(43)  评论(0)  编辑  收藏  举报