Complete implementation of AVL Tree in C Language

For more information about the AVL Tree, see "Examples.

The non-recursive method is adopted, which is efficient and has been tested.

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# Include typedef enum {EH = 0, LH = 1, RH =-1} bh_t; typedef enum {FALSE = 0, TRUE = 1} bool_t; typedef int ElemType; typedef struct BSTNode {ElemType key; int bf; struct BSTNode * lchild, * rchild, * parent;} BSTNode, * BSTree; bool_t searchAVL (BSTree root, ElemType key, BSTNode ** parent) {BSTNode * tmp = NULL; assert (root! = NULL); * parent = root-> parent; tmp = root; while (NULL! = Tmp) {if (tmp-> key = key) {return TRUE;} * parent = tmp; if (tmp-> key) {tmp = tmp-> lchild;} else {tmp = tmp-> rchild;} return FALSE;}/* get the minimum node */BSTNode * minNode (BSTNode * root) {if (root = NULL) {return NULL;} while (root-> lchild! = NULL) {root = root-> lchild;} return root;}/* get the maximum node */BSTNode * maxNode (BSTNode * root) {if (root = NULL) {return NULL;} while (root-> rchild! = NULL) {root = root-> rchild;} return root;}/* get the previous node */BSTNode * preNode (BSTNode * target) {if (target = NULL) {return NULL;} if (target-> lchild! = NULL) {return maxNode (target-> lchild) ;}while (target-> parent! = NULL) & (target! = Target-> parent-> rchild) {target = target-> parent;} return target-> parent ;} /* get the next node */BSTNode * nextNode (BSTNode * target) {if (target = NULL) {return NULL;} if (target-> rchild! = NULL) {return minNode (target-> rchild) ;}while (target-> parent! = NULL) & (target! = Target-> parent-> lchild) {target = target-> parent;} return target-> parent;} BSTNode * leftbalance (BSTNode * root, BSTNode * parent, BSTNode * child) {BSTNode * cur; assert (parent! = NULL) & (child! = NULL);/* LR */if (child-> bf = RH) {cur = child-> rchild; cur-> parent = parent-> parent; child-> rchild = cur-> lchild; if (cur-> lchild! = NULL) {cur-> lchild-> parent = child;} parent-> lchild = cur-> rchild; if (cur-> rchild! = NULL) {cur-> rchild-> parent = parent;} cur-> lchild = child; cur-> rchild = parent; child-> parent = cur; if (parent-> parent! = NULL) {if (parent-> lchild = parent) {parent-> lchild = cur ;} else {parent-> rchild = cur ;}} else {root = cur;} parent-> parent = cur; if (cur-> bf = EH) {parent-> bf = EH; child-> bf = EH;} else if (cur-> bf = RH) {parent-> bf = EH; child-> bf = LH;} else {parent-> bf = RH; child-> bf = EH;} cur-> bf = EH ;} /* LL */else {child-> parent = parent-> parent; parent-> lchild = child-> rchild; if (child-> rchil D! = NULL) {child-> rchild-> parent = parent;} child-> rchild = parent; if (parent-> parent! = NULL) {if (parent-> lchild = parent) {parent-> lchild = child ;} else {parent-> rchild = child;} else {root = child;} parent-> parent = child; /* when insert */if (child-> bf = LH) {child-> bf = EH; parent-> bf = EH ;} /* when delete */else {child-> bf = RH; parent-> bf = LH;} return root;} BSTNode * rightbalance (BSTNode * root, BSTNode * parent, BSTNode * child) {BSTNode * cur; assert (parent! = NULL) & (child! = NULL);/* RL */if (child-> bf = LH) {cur = child-> lchild; cur-> parent = parent-> parent; child-> lchild = cur-> rchild; if (cur-> rchild! = NULL) {cur-> rchild-> parent = child;} parent-> rchild = cur-> lchild; if (cur-> lchild! = NULL) {cur-> lchild-> parent = parent;} cur-> lchild = parent; cur-> rchild = child; child-> parent = cur; if (parent-> parent! = NULL) {if (parent-> lchild = parent) {parent-> lchild = cur ;} else {parent-> rchild = cur ;}} else {root = cur;} parent-> parent = cur; if (cur-> bf = EH) {parent-> bf = EH; child-> bf = EH;} else if (cur-> bf = LH) {parent-> bf = EH; child-> bf = RH;} else {parent-> bf = LH; child-> bf = EH;} cur-> bf = EH ;} /* RR */else {child-> parent = parent-> parent; parent-> rchild = child-> lchild; if (child-> lchild! = NULL) child-> lchild-> parent = parent; child-> lchild = parent; if (parent-> parent! = NULL) {if (parent-> lchild = parent) {parent-> lchild = child ;} else {parent-> rchild = child;} else {root = child;} parent-> parent = child; /* when insert */if (child-> bf = RH) {child-> bf = EH; parent-> bf = EH ;} /* when delete */else {child-> bf = LH; parent-> bf = RH;} return root;} BSTNode * insertNode (ElemType key, BSTNode * root) {BSTNode * parent = NULL, * cur = NULL, * child = NULL; asser T (root! = NULL);/* node exists */if (searchAVL (root, key, & parent) {return root;} cur = (BSTNode *) malloc (sizeof (BSTNode); cur-> parent = parent; cur-> key = key; cur-> lchild = NULL; cur-> rchild = NULL; cur-> bf = EH; if (key
     
      
Key) {parent-> lchild = cur; child = parent-> lchild;} else {parent-> rchild = cur; child = parent-> rchild ;} /* get the minimax tree needed to be adjusted */while (parent! = NULL) {if (child = parent-> lchild) {if (parent-> bf = RH) {parent-> bf = EH; return root ;} else if (parent-> bf = EH) {root = leftbalance (root, parent, child); break;} else {parent-> bf = LH; child = parent; parent = parent-> parent ;}} else {if (parent-> bf = LH) // It is the right child and will not cause imbalance {parent-> bf = EH; return root;} else if (parent-> bf = RH) // It is the right child and causes imbalance of parent {root = rightbalance (root, parent, child ); break;} else // Is the right child, and may cause parent's parent imbalance {parent-> bf = RH; child = parent; parent = parent-> parent ;}} return root ;} BSTNode * deleteNode (ElemType key, BSTNode * root) {BSTNode * dNode = NULL, * parent = NULL, * child = NULL; ElemType temp; assert (root! = NULL); if (! SearchAVL (root, key, & parent) {return root;} if (parent = NULL) {dNode = root;} else if (parent-> lchild! = NULL) & (parent-> lchild-> key = key) {dNode = parent-> lchild;} else {dNode = parent-> rchild ;} child = dNode; while (child-> lchild! = NULL) | (child-> rchild! = NULL) // determine the node to be deleted {if (child-> bf = LH) {child = preNode (dNode );} else {child = nextNode (dNode);} temp = child-> key; child-> key = dNode-> key; dNode-> key = temp; dNode = child ;} child = dNode; parent = dNode-> parent; while (parent! = NULL) // find the minimum subtree to be adjusted {if (child = parent-> lchild) {if (parent-> bf = LH) {parent-> bf = EH; child = parent; parent = parent-> parent;} else if (parent-> bf = RH) {child = parent-> rchild; root = rightbalance (root, parent, child); break;} else {parent-> bf = RH; break;} else {if (parent-> bf = RH) {parent-> bf = EH; child = parent; parent = parent-> parent;} else if (parent-> bf = LH) {child = parent-> lchild; root = left Balance (root, parent, child); break;} else {parent-> bf = LH; break ;}} if (dNode-> parent! = NULL) {if (dNode = dNode-> parent-> lchild) {dNode-> parent-> lchild = NULL ;} else {dNode-> parent-> rchild = NULL ;}} free (dNode); dNode = NULL; if (root = dNode) {root = NULL; // The root is deleted to avoid the wild pointer} return root;} BSTNode * createAVL (int * data, int size) {int I, j; BSTNode * root; if (size <1) {return NULL;} root = (BSTNode *) malloc (sizeof (BSTNode); root-> parent = NULL; root-> lchild = NULL; root-> rchild = NULL; root-> key = data [0]; root-> bf = 0; for (I = 1; I
      
        Lchild); destroyAVL (root-> rchild); free (root); root = NULL ;}} void InOrderTraverse (BSTree root) {if (NULL! = Root) {InOrderTraverse (root-> lchild); printf ("% d \ t", root-> key); InOrderTraverse (root-> rchild );}} void PreOrderTraverse (BSTree root) {if (NULL! = Root) {printf ("% d \ t", root-> key); PreOrderTraverse (root-> lchild); PreOrderTraverse (root-> rchild );}} int main (int argc, char * argv []) {int data [] = {1, 5, 7, 4, 3, 2, 11, 9, 10,100 }; BSTNode * root; root = createAVL (data, sizeof (data)/sizeof (data [0]); printf ("\ n ++ \ n "); inOrderTraverse (root); printf ("\ n"); PreOrderTraverse (root); root = deleteNode (5, root ); printf ("\ n ++ delete 5 ++ \ n"); InOrderTraverse (root ); printf ("\ n"); PreOrderTraverse (root); root = deleteNode (3, root ); printf ("\ n ++ delete 3 ++ \ n"); InOrderTraverse (root ); printf ("\ n"); PreOrderTraverse (root); root = deleteNode (1, root ); printf ("\ n ++ delete 1 ++ \ n"); InOrderTraverse (root ); printf ("\ n"); PreOrderTraverse (root); root = deleteNode (7, root ); printf ("\ n ++ delete 7 ++ \ n"); InOrderTraverse (root ); printf ("\ n"); PreOrderTraverse (root); root = deleteNode (4, root ); printf ("\ n ++ delete 4 ++ \ n"); InOrderTraverse (root ); printf ("\ n"); PreOrderTraverse (root); root = deleteNode (2, root ); printf ("\ n ++ delete 2 ++ \ n"); InOrderTraverse (root ); printf ("\ n"); PreOrderTraverse (root); printf ("\ n"); destroyAVL (root );}