# Data structure---C-language realization of Balanced binary tree (AVL tree)

Source: Internet
Author: User

`AVL (auto-balanced binary tree) #include <stdio.h> #include <stdlib.h>typedef int elemtype;//average typedef of each node enum{EH = 0, LH =                              1, RH =-1}bh_t;typedef enum{FALSE = 0, TRUE = 1}bool_t;//define Balanced binary tree typedef struct bstnode{elemtype key;//balance value int bf; struct Bstnode *lchild,*rchild;}  Bstnode, *bstree;//in sequence traversal void Inordertraverse (Bstree root) {if (NULL! = root) {inordertraverse (root->lchild);  printf ("%d\t", Root->key); Inordertraverse (Root->rchild);}}  The pre-order traversal of void Preordertraverse (Bstree root) {if (NULL! = root) {printf ("%d\t", Root->key);  Preordertraverse (Root->lchild); Preordertraverse (Root->rchild); }}//right-handed void R_rotate (Bstree *p) {bstree lc= (*p)->lchild; (*p)->lchild=lc->rchild; lc->rchild=*p; *P=LC;} L-void L_rotate (Bstree *p) {bstree rc= (*p)->rchild; (*p)->rchild=rc->lchild; rc->lchild=*p; *P=RC;} Make left balance void leftbalance (Bstree *t) {bstree lc= (*t)->lchild; Bstree rd = lc->rchild;  Determine which side to rotate switch (LC-&GT;BF) {case LH: (*t)->bf=lc->bf=eh;   R_rotate (T);  Break     Case Rh:switch (RD-&GT;BF) {case LH: (*t)->bf=rh;     lc->bf=eh;    Break     Case EH: (*t)->bf=lc->bf=eh;    Break     Case RH: (*t)->bf=eh;     lc->bf=lh;   Break   } rd->bf=eh;   L_rotate (& (*t)->lchild);   R_rotate (T); Break }}//make Right balance void rightbalance (Bstree *t) {bstree rc= (*t)->rchild; Bstree ld=rc->lchild;   Switch (RC-&GT;BF) {case RH: (*t)->bf=rc->bf=eh;   L_rotate (T);  Break     Case Lh:switch (LD-&GT;BF) {case RH: (*t)->bf=lh;     rc->bf=eh;    Break     Case EH: (*t)->bf=rc->bf=eh;    Break     Case LH: (*t)->bf=eh;     rc->bf=rh;   Break   } ld->bf=eh;   R_rotate (& (*t)->rchild);   L_rotate (T); Break }}//Insert Element bool_t Insertavl (bstree *t,elemtype e,bool_t *taller) {if (null = = t) return FALSE; if (null = = *t) {*t= (Bstree) m  Alloc (sizeof (Bstnode));  if (NULL = = *t) return FALSE;  (*t)->key=e; (*t)->lchild= (*t)->rchild=null;  (*t)->bf=eh; *taller=true;   } else {if (e== (*t)->key) {*taller=false;  return FALSE;   if (e< (*t)->key) {if (false = = Insertavl (& (*t)->lchild), E,taller) return FALSE;      if (*taller) {switch ((*t)->bf) {case lh:leftbalance (t);      *taller=false;     Break      Case EH: (*t)->bf=lh;      *taller=true;     Break      Case RH: (*t)->bf=eh;      *taller=false;    Break   }}} else {if (false = = Insertavl (& (*t)->rchild), E,taller) return FALSE;      if (*taller) {switch ((*t)->bf) {case rh:rightbalance (t);      *taller=false;     Break      Case EH: (*t)->bf=rh;      *taller=true;     Break      Case LH: (*t)->bf=eh;      *taller=false;    Break }}}} return TRUE;  Bstree Searchavl (Bstree t,elemtype key) {Bstree p=t; while (p) {if (P->key==key) return p;  else if (P->key<key) p=p->rchild; else p=p-&Gt;lchild; } return p;}  static void Destroy (Bstree *t) {if (NULL! = *t) {Destroy (& ((*t)->lchild));  Destroy (& (*t)->rchild);  Free (*t); *t = NULL; } return; void Destroyavl (Bstree root) {if (NULL! = root) {destroy (&root);} return;} int main () {Bstree root=null,r; bool_t taller=false; int array[]={13,24,37,90,53}; int i = 0; for (i=0; i < 5; i++) Ins Ertavl (&root,array[i],&taller); printf ("middle order traversal: \ n"); Inordertraverse (root); printf ("\ n-sequence traversal \ n"); Preordertraverse (Root);p rintf ("\ n search: 37\n"); R=searchavl (root,37); if (r) {printf ("%d\n", R->key),} else {printf ("not find!\n");} Destroyavl (Root); root = NULL; return 0;}`

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Data structure---C-language realization of Balanced binary tree (AVL tree)

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