二叉树遍历（递归实现）

先用比较笨的方法创建可以棵如下的树:

主要是用于后面的实验用，总的来讲，用递归实现遍历很简单。实现了三种遍历方法：先序遍历，中序遍历，后序遍历。以以上的树为例输出的结果应为：A, B, D, C, E, F; B, D, A, E, C, F; D, B, E, F, C, A.

/************************************************************************/ /* author : thomas E-mail: chenhua308@gmail.com */ /************************************************************************/

#include <stdio.h> #include <malloc.h> #include <string.h> #include <stdlib.h> typedef struct btnode{ //btnode - binary tree node struct btnode *Rchild; struct btnode *Lchild; char element; } BTNODE; /*typedef struct btree { struct btnode *Root; } BTree;*/ typedef BTNODE *BTree; //void (*visit)(BTNODE *Btnode); BTree creat() //用比较笨的方法创建一颗指定的树为了验证函数用 { BTNODE *temp, *root; root = (BTNODE *)malloc(sizeof(BTNODE)); root -> element = 'A'; root -> Lchild = (BTNODE *)malloc(sizeof(BTNODE)); temp = root -> Lchild; temp -> element = 'B'; temp -> Lchild = NULL; temp -> Rchild = (BTNODE *)malloc(sizeof(BTNODE)); temp -> Rchild -> element = 'D'; temp -> Rchild -> Lchild = NULL; temp -> Rchild -> Rchild = NULL; root -> Rchild = (BTNODE *)malloc(sizeof(BTNODE)); temp = root -> Rchild; temp -> element = 'C'; temp -> Lchild = (BTNODE *)malloc(sizeof(BTNODE)); temp -> Lchild -> element = 'E'; temp -> Lchild -> Lchild = NULL; temp -> Lchild -> Rchild = NULL; temp -> Rchild = (BTNODE *)malloc(sizeof(BTNODE)); temp -> Rchild -> element = 'F'; temp -> Rchild -> Lchild = NULL; temp -> Rchild -> Rchild = NULL; return root; } //访问函数 void visit(BTNODE *Btnode) { putchar(Btnode -> element); printf(" "); } //递归遍历 //先序遍历(VLR) void preOrd(void (*visit)(BTNODE *Btnode), BTree btree) { if ( btree ) { visit( btree ); preOrd( visit, btree -> Lchild ); preOrd( visit, btree -> Rchild ); } } //中序遍历(LVR) void MidOrd(void (*visit)(BTNODE *Btnode), BTree btree) { if ( btree ) { MidOrd( visit, btree -> Lchild ); visit( btree ); MidOrd( visit, btree -> Rchild ); } } //后续遍历(LRV) void PostOrd(void (*visit)(BTNODE *Btnode), BTree btree) { if ( btree ) { PostOrd( visit, btree -> Lchild ); PostOrd( visit, btree -> Rchild ); visit( btree ); } } //compute the number of tree int size(BTree btree) { int s, s1, s2; if (!btree) return 0; else { s1 = size( btree -> Lchild ); s2 = size( btree -> Rchild ); s = s1 + s2 +1; return s; } } //compute the height int depth(BTree btree) { if (!btree) return 0; else return 1 + max(depth(btree -> Lchild), depth(btree -> Rchild)); } //test functions void main(int argc, char *argv[]) { BTree btree; int num; btree = creat(); preOrd( visit, btree ); printf("/n"); MidOrd( visit, btree ); printf("/n"); PostOrd( visit, btree ); printf("/n"); num = size(btree); printf("%d /n", num); num = depth(btree); printf("%d /n", num); }