Treap树实现文件C语言

 对于这个,想说的是.关于 NullNode 结点.在调用Release ()释放内存之后,要将其恢复为NULL,以便下次的连续使用.自己想到的,很不错.

/* treap.c -- treap树实现文件 */ #include "treapTree.h" /* 全局变量声明定义 */ static Node * NullNode = NULL ; /* 局部函数声明 */ static Node * singleRotateWithLeft (Node * const pn) ; static Node * singleRotateWithRight (Node * const pn) ; static void release (const TreapTree tt) ; /* 接口函数定义 */ TreapTree Initialize_T (void) { if (NULL == NullNode) { NullNode = (Node *) malloc (sizeof (Node)) ; if (NULL == NullNode) return NULL ; NullNode -> left = NullNode -> right = NullNode ; NullNode -> priority = INFINITY ; srand ((unsigned int) time (NULL)) ; } return NullNode ; } TreapTree Insert_T (TreapTree tt, const Item item) { if (tt == NullNode) { /* Create and return a one-node tree. */ tt = (Node *) malloc (sizeof (Node)) ; if (NULL == tt) puts ("Out of space.") ; else { tt -> item = item ; tt -> priority = rand () ; tt -> left = tt -> right = NullNode ; } } else if (item < tt -> item) { tt -> left = Insert_T (tt -> left, item) ; if (tt -> left -> priority < tt -> priority) tt = singleRotateWithLeft (tt) ; } else if (item > tt -> item) { tt -> right = Insert_T (tt -> right, item) ; if (tt -> right -> priority < tt -> priority) tt = singleRotateWithRight (tt) ; } /* Otherwise it's a duplicate, do nothing. */ return tt ; } TreapTree Delete_T (TreapTree tt, const Item item) { if (tt != NullNode) { if (item < tt -> item) tt -> left = Delete_T (tt -> left, item) ; else if (item > tt -> item) tt -> right = Delete_T (tt -> right, item) ; else { /* Match found. */ if (tt -> left -> priority < tt -> right -> priority) tt = singleRotateWithLeft (tt) ; else tt = singleRotateWithRight (tt) ; if (tt != NullNode) /* Continue on down. */ tt = Delete_T (tt, item) ; else { /* At a leaf. */ free (tt -> left) ; tt -> left = NullNode ; } } } return tt ; } void Release_T (const TreapTree tt) { release (tt) ; free (NullNode) ; /* For next Initialize_T (). */ NullNode = NULL ; } /* 局部函数定义 */ static Node * singleRotateWithLeft (Node * const pn) { Node * child ; child = pn -> left ; pn -> left = child -> right ; child -> right = pn ; return child ; } static Node * singleRotateWithRight (Node * const pn) { Node * child ; child = pn -> right ; pn -> right = child -> left ; child -> left = pn ; return child ; } static void release (const TreapTree tt) { if (tt != NullNode) { release (tt -> left) ; release (tt -> right) ; free (tt) ; } }