二叉树的建立与遍历（C语言简单实现）

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAXSIZE 1024

//二叉树节点
typedef struct tNode{
char data;
tNode *lchild;
tNode *rchild;
}bitree;

//调用函数声明
bitree * Create();
int LayerTraverse();
int InOrder();
int PreOrder();

//建立二叉树
bitree * Create(){
char ch;
bitree *root,*s;
printf("Please input the char\nIf it's null input '@'\nEnd with '#'\n");
bitree *Q[MAXSIZE];
int front, rear;
root = NULL; front = 1; rear = 0;
getchar();
while ((ch = getchar())!='#')
{
s = NULL;
if (ch != '@'){
s = (bitree *)malloc(sizeof(bitree));
s->data = ch;
s->lchild = NULL;
s->rchild = NULL;

}
rear++;
Q[rear] = s;
if (rear == 1) root = s;
else{
if (s && Q[front]){
if (rear % 2 == 0) Q[front]->lchild = s;
else Q[front]->rchild = s;
}
if (rear % 2 == 1) front++;
}

}
return root;

}

//广度遍历二叉树
int LayerTraverse(bitree *head){

int front, rear;
bitree *Q[MAXSIZE];
bitree *s;
if (head != NULL){
rear = 1; front = 0;
Q[rear] = head;
while (front < rear){
front++;
s = Q[front];
printf("%c ",s->data);
if (s->lchild != NULL){
rear++;
Q[rear] = s->lchild;

}
if (s->rchild != NULL){
rear++;
Q[rear] = s->rchild;
}
}

}

getchar();
return 0;
}

//中序非递归遍历
int InOrder(bitree *head){
int top;
bitree *stack[MAXSIZE];
bitree *s;
if (head != NULL){
top = -1;
s = head;
while ((top != -1) || (s != NULL)){
while (s!=NULL)
{
if (top == MAXSIZE - 1){
printf("overflow\n");
return 0;
}
else
{
top++;
stack[top] = s;
s = s->lchild;
}

}
s = stack[top];
top--;
printf("%c ",s->data);
s = s->rchild;
}
}

return 0;
}

//前序递归遍历
int PreOrder(bitree *head){

if (head != NULL){
printf("%c ",head->data);
PreOrder(head->lchild);
PreOrder(head->rchild);
}
return 0;
}

//
int main(){

int select;
bitree *head1,*head2;
head1 = head2 = NULL;

do{
printf("\n*******************************\n");
printf("\nPress to select function:\n");
printf("\n1 to build a bitree\n");
printf("\n2 to layer traversal\n");
printf("\n3 to middle traversal\n");
printf("\n4 to front traversal\n");
printf("\n0 to exit\n");
printf("\n*******************************\n\n");

scanf_s("%d",&select);

if (select < 0 || select>5){
printf("Input error.Please input again\n");
continue;
}
switch (select)
{
case 0:{
return 0;
}
case 1:{
printf("The bitree you want to build in layer traversal order:\n");
head1 = Create();
LayerTraverse(head1);
getchar();
break;
}
case 2:{
printf("Layer traversal:\n");
LayerTraverse(head1);
getchar();
break;
}
case 3:{
printf("InOrder traversal:\n");
InOrder(head1);
getchar();
break;
}
case 4:{
printf("PreOrder traversal:\n");
PreOrder(head1);
getchar();
break;
}

default:
break;
}
} while (select != 0);

return 0;
}