D堆的实现

来源：互联网发布：lindsey stirling 知乎编辑：程序博客网时间：2024/05/18 18:01
实现上一篇博客(http://blog.csdn.net/buleriver/article/details/38469977)说的D堆，如果把mD设置成2，D堆就退化成二叉堆，也就是说，二叉堆是D堆的一种情况。
public class DHeap {      public static final int INIT_CAPACITY = 10;      private int[] mArray;      private int mLength;      private final int mD;            public DHeap(int d) {          mArray = new int[INIT_CAPACITY + 1];          mLength = 0;          mD = d;      }            public int getParentIndex(int index) {          return (index - 2 + mD) / mD;      }            public int getChildIndex(int pIndex, int childIndex) {          return mD * (pIndex - 1) + 2 + childIndex;      }            private void expandArray(int length) {          int[] arr = new int[length];          System.arraycopy(mArray, 1, arr, 1, mLength);          mArray = arr;      }            /**      * 自下而上，把value放到最后一个，然后一直和其父节点交换，找到合适的位置      */      public void insert(int value) {          if (mLength >= mArray.length - 1) {              expandArray(mArray.length * 2);          }          mArray[++mLength] = value;          int index = mLength;          int parentIndex = getParentIndex(index);          while (parentIndex > 0) {              int currentValue = mArray[index];              int parentValue = mArray[parentIndex];              if (currentValue < parentValue) {                  mArray[parentIndex] = currentValue;                  mArray[index] = parentValue;                  index = parentIndex;                  parentIndex = getParentIndex(index);              } else {                  break;              }          }      }            public void deleteMin() {          if (mLength <= 0) {              return;          } else if (mLength == 1) {              mLength--;          } else {              mArray[1] = mArray[mLength];              int index = 1;              mLength--;              while (true) {                  int value = mArray[index];                  int minIndex = -1;  // 最小孩子的数组索引                  boolean lastLevel = false;  // 是否已经到了最底层                  int firstChildIndex = getChildIndex(index, 0);                  int lastChildIndex = firstChildIndex + mD;                  for (int childIndex = firstChildIndex; childIndex < lastChildIndex; childIndex++) {  // 找到最小的孩子                      if (childIndex > mLength) {  // 已经到了最后一个                          lastLevel = true;                          break;                      }                      int childValue = mArray[childIndex];                      if (value > childValue) {                          value = childValue;                          minIndex = childIndex;                      }                  }                  if (minIndex < 0) {  // 已经符合d堆的性质，不需要置换了                      break;                  } else { // 需要置换                      mArray[minIndex] = mArray[index];                      mArray[index] = value;                      index = minIndex;                  }                  if (lastLevel) {    // 已经到了最底层                      break;                  }              }          }      }  }
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