1.树节点的典型声明

typedef struct TreeNode *PtrToNode;struct TreeNode{ElementType Element;PtrToNode     FirstChild;PtrToNode     NextSibling;      /* 指向下一个兄弟 */}

2.而叉查找树的实现

#include <stdio.h>
#include <stdlib.h>struct TreeNode;
typedef struct TreeNode *SearchTree;
typedef struct TreeNode *Position;struct TreeNode
{int Element;SearchTree Left;SearchTree Right;
};/* 清空＆初始化树 */
SearchTree MakeEmpty(SearchTree T)
{if (T != NULL){   MakeEmpty(T->Left);MakeEmpty(T->Right);free(T);}   return NULL;
}/* 在树中查找x */
Position Find(int x, SearchTree T)
{if (T == NULL)return NULL;if (x < T->Element)return Find(x, T->Left);else if (x > T->Element)return Find(x, T->Right);elsereturn T;
}/* 递归实现 */
Position FindMin(SearchTree T)
{if (T == NULL)return NULL;else if (T->Left == NULL)return T;elsereturn FindMin(T->Left);
}/* 非递归实现 */
Position FindMax(SearchTree T)
{if (T != NULL)while (T->Right != NULL)T = T->Right;return T;
}/* 将元素插入树 */
SearchTree Insert(int x, SearchTree T)
{if (T == NULL){T = malloc(sizeof(struct TreeNode));if (T == NULL)printf("Out of space!\n");else{T->Element = x;T->Left = T->Right = NULL;}}else if (x < T->Element)T->Left = Insert(x, T->Left);else if (x > T->Element)T->Right = Insert(x, T->Right);return T;
}/* 在树中查找x,并删除 */
SearchTree Delete(int x, SearchTree T)
{Position TmpCell;if (T == NULL)printf("Element not found!\n");else if (x < T->Element)T->Left = Delete(x, T->Left);else if (x < T->Element)T->Right = Delete(x, T->Right);else if (T->Left && T->Right){TmpCell = FindMin(T->Right);T->Element = TmpCell->Element;T->Right = Delete(T->Element, T->Right);}else{TmpCell = T;if (T->Left == NULL)T = T->Right;else if (T->Right == NULL)T = T->Left;free(TmpCell);}return T;
}int main()
{SearchTree tree = NULL;MakeEmpty(tree);/* 注意Insert返回值为树 */tree = Insert(3, tree);tree = Insert(1, tree);tree = Insert(2, tree);tree = Insert(4, tree);Position p;p = FindMin(tree);printf("Min = %d\n", p->Element);p = FindMax(tree);printf("Max = %d\n", p->Element);p = Find(1, tree);if (p != NULL){printf("Find %d success!\n", p->Element);}else{printf("Do not find in tree!\n");}tree = Delete(1, tree);p = FindMin(tree);printf("Min = %d\n", p->Element);return 0;
}