Insertion into Heap

insert will place a new element in the next available array position; this keeps the binary tree complete.

To maintain the heap order property, we must percolate up the new value until it reaches its proper position. This is easy: if the new item is less than its parent, swap the new item with its parent; then percolate up from the parent.

public void insert( AnyType item ) {
  if ( currentSize >= array.length - 1 )
     enlargeArray( array.length * 2 + 1 );
  int hole = ++currentSize;
  while ( hole > 1 &&
          item.compareTo( array[hole / 2] ) < 0 )
    { array[hole] = array[hole / 2];     // swap
      hole /= 2; }      // change hole to parent
  array[hole] = item; }

This is simple and gives O(log(n)) insert.