#include "leftheap.h"        #include "fatal.h"        #include <stdlib.h>        struct TreeNode        {            ElementType   Element;            PriorityQueue Left;            PriorityQueue Right;            int           Npl;        };        PriorityQueue        Initialize( void )        {            return NULL;        }        static PriorityQueue Merge1( PriorityQueue H1, PriorityQueue H2 );/* START: fig6_26.txt */        PriorityQueue        Merge( PriorityQueue H1, PriorityQueue H2 )        {/* 1*/      if( H1 == NULL )/* 2*/          return H2;/* 3*/      if( H2 == NULL )/* 4*/          return H1;/* 5*/      if( H1->Element < H2->Element )/* 6*/          return Merge1( H1, H2 );            else/* 7*/          return Merge1( H2, H1 );        }/* END */        void        SwapChildren( PriorityQueue H )        {            PriorityQueue Tmp;            Tmp = H->Left;            H->Left = H->Right;            H->Right = Tmp;        }/* START: fig6_27.txt */        static PriorityQueue        Merge1( PriorityQueue H1, PriorityQueue H2 )        {/* 1*/      if( H1->Left == NULL )  /* Single node *//* 2*/          H1->Left = H2;      /* H1->Right is already NULL,                                       H1->Npl is already 0 */            else            {/* 3*/          H1->Right = Merge( H1->Right, H2 );/* 4*/          if( H1->Left->Npl < H1->Right->Npl )/* 5*/              SwapChildren( H1 );/* 6*/          H1->Npl = H1->Right->Npl + 1;            }/* 7*/      return H1;        }/* END *//* START: fig6_29.txt */        PriorityQueue        Insert1( ElementType X, PriorityQueue H )        {            PriorityQueue SingleNode;/* 1*/      SingleNode = malloc( sizeof( struct TreeNode ) );/* 2*/      if( SingleNode == NULL )/* 3*/          FatalError( "Out of space!!!" );            else            {/* 4*/          SingleNode->Element = X; SingleNode->Npl = 0;/* 5*/          SingleNode->Left = SingleNode->Right = NULL;/* 6*/          H = Merge( SingleNode, H );            }/* 7*/      return H;        }/* END *//* START: fig6_30.txt */        /* DeleteMin1 returns the new tree; */        /* To get the minimum, use FindMin */        /* This is for convenience */        PriorityQueue        DeleteMin1( PriorityQueue H )        {            PriorityQueue LeftHeap, RightHeap;/* 1*/      if( IsEmpty( H ) )            {/* 2*/          Error( "Priority queue is empty" );/* 3*/          return H;            }/* 4*/      LeftHeap = H->Left;/* 5*/      RightHeap = H->Right;/* 6*/      free( H );/* 7*/      return Merge( LeftHeap, RightHeap );        }/* END */        ElementType        FindMin( PriorityQueue H )        {            if( !IsEmpty( H ) )                return H->Element;            Error( "Priority Queue is Empty" );            return  0;        }        int        IsEmpty( PriorityQueue H )        {            return H == NULL;        }