二叉树 创建 释放 遍历

前序遍历：ABDGHCEIF

中序遍历：GDHBAEICF

后序遍历：GHDBIEFCA

理解遍历：

void in_Order(BiTNode * root)    //先序遍历{    if(root == NULL)    {        return ;    }    printf("this is node %d\n",root->data);    in_Order(root->lchild);//遍历左子树printf("node %d finish scanning left.\n",root->data);    in_Order(root->rchild);//遍历右子树printf("node %d finish scanning right.\n",root->data);}int  main(){BiTNode *p1 = (BiTNode *)malloc(sizeof(BiTNode));memset(p1,0,sizeof(BiTNode));p1->data = 1;        BiTNode *p2 = (BiTNode *)malloc(sizeof(BiTNode));memset(p2,0,sizeof(BiTNode));p2->data = 2;BiTNode *p3 = (BiTNode *)malloc(sizeof(BiTNode));memset(p3,0,sizeof(BiTNode));p3->data = 3;BiTNode *p4 = (BiTNode *)malloc(sizeof(BiTNode));memset(p4,0,sizeof(BiTNode));p4->data = 4;p1->lchild = p2;p2->rchild = p3;p1->rchild = p4;        in_Order(p1);                return 0;}结果输出：this is node 1this is node 2node 2 finish scanning left.this is node 3node 3 finish scanning left.node 3 finish scanning right.node 2 finish scanning right.node 1 finish scanning left.this is node 4node 4 finish scanning left.node 4 finish scanning right.node 1 finish scanning right.请按任意键继续. . .

以下使用图上的前6个节点，1-2-3-4-5-6来创建二叉树；

1、二叉树的创建之关系创建（对象，需要使用memset初始化对象指针）

#include<stdio.h>#include <stdlib.h>#include <string.h>typedef struct BiTNode {int data;struct BiTNode *lchild;struct BiTNode *rchild;}BiTNode, *BiTree;//推导//struct BiTNode//{//  int data;//  struct BitNode *lchild;//  struct BiTNode *rchild;//};//typedef struct BiTNode  BiTNode;//typedef struct BiTNode* BiTree;int main(){//create nodeBiTNode t1; BiTNode t2;BiTNode t3; BiTNode t4;BiTNode t5; BiTNode t6;     memset(&t1,0,sizeof(BiTNode)); t1.data = 1; memset(&t2,0,sizeof(BiTNode)); t2.data = 2;memset(&t3,0,sizeof(BiTNode)); t3.data = 3;memset(&t4,0,sizeof(BiTNode)); t4.data = 4;memset(&t5,0,sizeof(BiTNode)); t5.data = 5;memset(&t6,0,sizeof(BiTNode)); t6.data = 6; t1.lchild = &t2;t1.rchild = &t3;t2.lchild = &t4;t2.rchild = &t5;t3.lchild = &t6;return 0;}

2、二叉树的创建之关系创建（指针，需要使用memset初始化指针）

#include<stdio.h>#include <stdlib.h>#include <string.h>struct BiTNode {int data;struct BiTNode *lchild;struct BiTNode *rchild;};typedef struct BiTNode  BiTNode;typedef struct BiTNode* BiTree;int main(){//create nodeBiTNode *p1 = (BiTNode *)malloc(sizeof(BiTNode)); memset(p1,0, sizeof(BiTNode));p1->data = 1;BiTNode *p2 = (BiTNode *)malloc(sizeof(BiTNode)); memset(p2,0, sizeof(BiTNode));p2->data = 2;BiTNode *p3 = (BiTNode *)malloc(sizeof(BiTNode));memset(p3,0, sizeof(BiTNode));p3->data = 3;BiTNode *p4 = (BiTNode *)malloc(sizeof(BiTNode)); memset(p4,0, sizeof(BiTNode));p4->data = 4;BiTNode *p5 = (BiTNode *)malloc(sizeof(BiTNode));memset(p5,0, sizeof(BiTNode));p5->data = 5;BiTNode *p6 = (BiTNode *)malloc(sizeof(BiTNode)); memset(p6,0, sizeof(BiTNode));p6->data = 6;p1->lchild = p2;p1->rchild = p3;p2->lchild = p4;p2->rchild = p5;p3->lchild = p6;return 0;}

3、二叉树创建之使用全局变量（三个遍历）

#include<stdio.h>#include <stdlib.h>#include <string.h>struct BiTNode {int pdata;int ldata;int rdata;};typedef struct BiTNode  BiTNode;#define MAX 1000#define NIL -1BiTNode Node[MAX] ; //节点int n = 6;//共6个节点void preParse(int root){if(Node[root].pdata == NIL)return;printf("%d ",Node[root].pdata);preParse(Node[root].ldata);preParse(Node[root].rdata);}void postParse(int root){if(Node[root].pdata == NIL)return;postParse(Node[root].ldata);postParse(Node[root].rdata);printf("%d ",Node[root].pdata);}void inParse(int root){if(Node[root].pdata == NIL)return;inParse(Node[root].ldata);printf("%d ",Node[root].pdata);inParse(Node[root].rdata);}int main(){//create node    int i;for(i = 1; i <= n; i++){Node[i].pdata = NIL;Node[i].ldata = NIL;Node[i].rdata = NIL;}Node[1].pdata = 1;Node[2].pdata = 2;Node[3].pdata = 3;Node[4].pdata = 4;Node[5].pdata = 5;Node[6].pdata = 6;Node[1].ldata = Node[2].pdata;Node[1].rdata = Node[3].pdata;Node[2].ldata = Node[4].pdata;Node[2].rdata = Node[5].pdata;Node[3].ldata = Node[6].pdata;//前序遍历preParse(1);printf("\n");//后序遍历postParse(1);printf("\n");//中序遍历inParse(1);return 0;}

4、二叉树创建之使用#（没有子节点的用”#“替代，前序创建二叉树）包含二叉树的释放，使用后序遍历释放

#include <stdio.h>#include <stdlib.h>#include <string.h> typedef struct BiTNode{    int data;    struct BiTNode *lchild;    struct BiTNode *rchild;}BiTNode,*BiTree; void in_Order(BiTNode * root)    //先序遍历{    if(root == NULL)    {        return ;    }    printf("%c",root->data);    in_Order(root->lchild);//遍历左子树    in_Order(root->rchild);//遍历右子树} BiTNode* create_tree()//先序创建{    BiTNode *node = NULL;    BiTNode *pleft  = NULL;    BiTNode *pright = NULL;    char c = getchar();     if(c == '#')    {        return NULL;    }    else    {        node = (BiTNode*)malloc(sizeof(BiTNode));        memset(node,0,sizeof(BiTNode));        node->data = c;         pleft = create_tree();        if(pleft != NULL)        {            node->lchild = pleft;        }        else        {            node->lchild = NULL;        }                 pright = create_tree();        if(pleft != NULL)        {            node->rchild = pright;        }        else        {            node->rchild = NULL;        }    }    return node;  } void free_tree(BiTNode* T)//后序释放{    if(!T)    {        return ;    }    if(T->lchild)    {        free_tree(T->lchild);        //T->lchild = NULL;    }    if(T->rchild)    {        free_tree(T->rchild);        //T->rchild = NULL;    }    if(T)    {        free(T);        T = NULL;    }} int  main(){    BiTNode *p = create_tree();     in_Order(p);              printf("\n"); //释放空间    free_tree(p);    return 0;}输入与结果:124##5##36###124536

5.二叉树的层序遍历

5、计算叶子节点的数目；（无论是先序遍历,中序遍历,后序遍历,求叶子的数字都不变;因为本质都是一样的,任何一个节点都会遍历3趟）

#include <stdio.h>#include <stdlib.h>#include <string.h>typedef struct BiTNode{    int data;    struct BiTNode *lchild;    struct BiTNode *rchild;}BiTNode,*BiTree; void pre_Order(BiTNode * root)   //先序遍历{    if(root == NULL)    {        return ;    }    printf("%d ",root->data);    pre_Order(root->lchild);//遍历左子树    pre_Order(root->rchild);//遍历右子树} void in_Order(BiTNode * root)    //中序遍历{    if(root == NULL)    {        return ;    }    in_Order(root->lchild);//遍历左子树    printf("%d ",root->data);    in_Order(root->rchild);//遍历右子树} void post_Order(BiTNode * root)  //后序遍历{    if(root == NULL)    {        return ;    }    post_Order(root->lchild);//遍历左子树    post_Order(root->rchild);//遍历右子树    printf("%d ",root->data);} void count_leaf(BiTNode * root,int * num)   {    if(!root)    {        return ;    }    if(!root->rchild && !root->rchild)//当左右孩子都为空    {        (*num)++;    }    if(root->lchild)    {        count_leaf(root->lchild,num);//遍历左子树    }    if(root->rchild)    {        count_leaf(root->rchild,num);//遍历右子树    }    return ;}int main(){    //创建节点    BiTNode t1;    memset(&t1,0,sizeof(BiTNode));  t1.data = 1;    BiTNode t2;    memset(&t2,0,sizeof(BiTNode));  t2.data = 2;    BiTNode t3;    memset(&t3,0,sizeof(BiTNode));  t3.data = 3;    BiTNode t4;    memset(&t4,0,sizeof(BiTNode));  t4.data = 4;    BiTNode t5;    memset(&t5,0,sizeof(BiTNode));  t5.data = 5;    //建立关系    t1.lchild = &t2;    t1.rchild = &t3;    t2.lchild = &t4;    t3.lchild = &t5;     //树的遍历    pre_Order(&t1);     printf("    先序遍历\n");    in_Order(&t1);      printf("    中序遍历\n");    post_Order(&t1);    printf("    后序遍历\n");     int num = 0;    count_leaf(&t1,&num);   //解决多线程,资源竞争问题    printf("叶子节点的个数 %d\n",num);     return 0;}

6.计算二叉树的高度

#include <stdio.h>#include <stdlib.h>#include <string.h>typedef struct BiTNode{    int data;    struct BiTNode *lchild;    struct BiTNode *rchild;}BiTNode,*BiTree; int tree_dept(BiTNode * root){    int depth_left = 0;    int depth_right = 0;    if(!root)    {        return 0;    }    depth_left = tree_dept(root->lchild);    depth_right = tree_dept(root->rchild);    return  1+(depth_left>depth_right ? depth_left:depth_right);}int main(){    //创建节点    BiTNode t1;    memset(&t1,0,sizeof(BiTNode));  t1.data = 1;    BiTNode t2;    memset(&t2,0,sizeof(BiTNode));  t2.data = 2;    BiTNode t3;    memset(&t3,0,sizeof(BiTNode));  t3.data = 3;    BiTNode t4;    memset(&t4,0,sizeof(BiTNode));  t4.data = 4;    BiTNode t5;    memset(&t5,0,sizeof(BiTNode));  t5.data = 5;    BiTNode t6;    memset(&t6,0,sizeof(BiTNode));  t6.data = 6;    //建立关系    t1.lchild = &t2;    t1.rchild = &t3;    t2.lchild = &t4;    t3.lchild = &t5;    t2.rchild = &t6;     int depth = 0;    depth = tree_dept(&t1);      printf("树的高度 %d\n",depth);     return 0;}