tree.h
typedef struct TreeNode_s {char val;//数据域struct TreeNode_s *pLeft;//左结点struct TreeNode_s *pRight;//右边结点
} TreeNode_t, *pTreeNode_t;//辅助队列建立二叉树
typedef struct QueueNode_s {pTreeNode_t NodeAddr; //数据域存储一个二叉树结点的地址 struct QueueNode_s *pNext;
} QueueNode_t, *pQueueNode_t;void preOrder(pTreeNode_t pRoot);
void inOrder(pTreeNode_t pRoot);
void postOrder(pTreeNode_t pRoot);
void buildBinaryTree(pTreeNode_t *ppRoot, pQueueNode_t *ppQueueFront, pQueueNode_t *ppQueueRear, char val);
main.c
#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "tree.h"
#define N 10
int main() {//char c[] = "ABCDEFGHIJ";//pTreeNode_t arr[N] = { NULL };//索引数组//for (int i = 0; i < N; ++i) {// arr[i] = (pTreeNode_t)calloc(1, sizeof(TreeNode_t));// arr[i]->val = c[i];//}//pTreeNode_t pRoot = arr[0];//for (int i = 0, j = 1; j < N; ++j) {// if (arr[i]->pLeft == NULL) {// arr[i]->pLeft = arr[j];// }// else {// arr[i]->pRight = arr[j];// ++i;// }//}pTreeNode_t pRoot = NULL;pQueueNode_t pQueueFront = NULL;pQueueNode_t pQueueRear = NULL;char val;while (scanf("%c", &val) != EOF) {if (val == '\n') {break;}buildBinaryTree(&pRoot, &pQueueFront, &pQueueRear, val);}preOrder(pRoot);printf("\n");inOrder(pRoot);printf("\n");postOrder(pRoot);printf("\n");
}//三种树的遍历方式
void preOrder(pTreeNode_t pRoot) {if (pRoot) {printf("%c", pRoot->val);preOrder(pRoot->pLeft);preOrder(pRoot->pRight);}
}
void inOrder(pTreeNode_t pRoot) {if (pRoot) {inOrder(pRoot->pLeft);printf("%c", pRoot->val);inOrder(pRoot->pRight);}
}
void postOrder(pTreeNode_t pRoot) {if (pRoot) {postOrder(pRoot->pLeft);postOrder(pRoot->pRight);printf("%c", pRoot->val);}
}//利用辅助队列层次建立二叉树
void buildBinaryTree(pTreeNode_t *ppRoot, pQueueNode_t *ppQueueFront, pQueueNode_t *ppQueueRear, char val) {pTreeNode_t pTreeNode = (pTreeNode_t)calloc(1, sizeof(TreeNode_t));pTreeNode->val = val;pQueueNode_t pQueueNode = (pQueueNode_t)calloc(1, sizeof(QueueNode_t));pQueueNode->NodeAddr = pTreeNode;if (*ppRoot == NULL) {//给二叉树和队列插入第一个结点*ppRoot = pTreeNode;*ppQueueFront = pQueueNode;*ppQueueRear = pQueueNode;}else {//用尾插法入队(*ppQueueRear)->pNext = pQueueNode;*ppQueueRear = pQueueNode;pQueueNode_t pQueueCur = *ppQueueFront;//队首if (pQueueCur->NodeAddr->pLeft == NULL) {//把新结点插入到队首所指的二叉树结点的左孩子pQueueCur->NodeAddr->pLeft = pTreeNode;}else {pQueueCur->NodeAddr->pRight = pTreeNode;//放好右孩子之后，要出队*ppQueueFront = pQueueCur->pNext;free(pQueueCur);pQueueCur = NULL;}}
}
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