/*
** Convert a sorted list of elements (connected by pRight) into a binary
** tree with depth of iDepth. A depth of 1 means the tree contains a single
** node taken from the head of *ppList. A depth of 2 means a tree with
** three nodes. And so forth.
**
** Use as many entries from the input list as required and update the
** *ppList to point to the unused elements of the list. If the input
** list contains too few elements, then construct an incomplete tree
** and leave *ppList set to NULL.
**
** Return a pointer to the root of the constructed binary tree.
*/
static struct RowSetEntry *rowSetNDeepTree(
struct RowSetEntry **ppList,
int iDepth
){
struct RowSetEntry *p; /* Root of the new tree */
struct RowSetEntry *pLeft; /* Left subtree */
if( *ppList==0 ){
return 0;
}
if( iDepth==1 ){
p = *ppList;
*ppList = p->pRight;
p->pLeft = p->pRight = 0;
return p;
}
pLeft = rowSetNDeepTree(ppList, iDepth-1);
p = *ppList;
if( p==0 ){
return pLeft;
}
p->pLeft = pLeft;
*ppList = p->pRight;
p->pRight = rowSetNDeepTree(ppList, iDepth-1);
return p;
}
/*
** Convert a sorted list of elements (connected by pRight) into a binary
** tree with depth of iDepth. A depth of 1 means the tree contains a single
** node taken from the head of *ppList. A depth of 2 means a tree with
** three nodes. And so forth.
**
** Use as many entries from the input list as required and update the
** *ppList to point to the unused elements of the list. If the input
** list contains too few elements, then construct an incomplete tree
** and leave *ppList set to NULL.
**
** Return a pointer to the root of the constructed binary tree.
*/
static struct RowSetEntry *rowSetNDeepTree(
struct RowSetEntry **ppList,
int iDepth
){
struct RowSetEntry *p; /* Root of the new tree */
struct RowSetEntry *pLeft; /* Left subtree */
if( *ppList==0 ){ /*OPTIMIZATION-IF-TRUE*/
/* Prevent unnecessary deep recursion when we run out of entries */
return 0;
}
if( iDepth>1 ){ /*OPTIMIZATION-IF-TRUE*/
/* This branch causes a *balanced* tree to be generated. A valid tree
** is still generated without this branch, but the tree is wildly
** unbalanced and inefficient. */
pLeft = rowSetNDeepTree(ppList, iDepth-1);
p = *ppList;
if( p==0 ){ /*OPTIMIZATION-IF-FALSE*/
/* It is safe to always return here, but the resulting tree
** would be unbalanced */
return pLeft;
}
p->pLeft = pLeft;
*ppList = p->pRight;
p->pRight = rowSetNDeepTree(ppList, iDepth-1);
}else{
p = *ppList;
*ppList = p->pRight;
p->pLeft = p->pRight = 0;
}
return p;
}
/*
** Convert a sorted list of elements into a binary tree. Make the tree
** as deep as it needs to be in order to contain the entire list.
*/
static struct RowSetEntry *rowSetListToTree(struct RowSetEntry *pList){
int iDepth; /* Depth of the tree so far */
struct RowSetEntry *p; /* Current tree root */
struct RowSetEntry *pLeft; /* Left subtree */
assert( pList!=0 );
p = pList;
pList = p->pRight;
p->pLeft = p->pRight = 0;
for(iDepth=1; pList; iDepth++){
pLeft = p;
p = pList;
pList = p->pRight;
p->pLeft = pLeft;
p->pRight = rowSetNDeepTree(&pList, iDepth);
}
return p;
}
