binary_tree/btree.c

#include <stdio.h>
#include <stdlib.h>
#include "btree.h"
#include "linkqueue.h"

btree_t pkt_creat_btree(void)
{
    btree_t n;
    data_type data;
    scanf("%lc", &data);
    if('#' == data)
    {
        return NULL; /* 开始递归调用返回，返回到最后一层 pkt_prev_order() 调用处，子树指针被赋值为NULL */
    }
    else
    {
        if((n = (btree_t)malloc(sizeof(struct btree))) == NULL)
        {
            printf("malloc failed!\n");
            return NULL;
        }
        n->data = data;
        n->lchild = pkt_creat_btree();  /* 开始递归调用 */
        n->rchild = pkt_creat_btree();
    }
    return n;
}

/* 先序遍历 */
void pkt_prev_order(btree_t t)
{
    if(t != NULL)
    {
        printf("%lc\n", t->data);  /* 访问节点 */
        pkt_prev_order(t->lchild); /* 递归遍历左子树 */
        pkt_prev_order(t->rchild); /* 递归遍历右子树 */
    }
}

/* 中序遍历 */
void pkt_mid_order(btree_t t)
{
    if(t != NULL)
    {
        pkt_mid_order(t->lchild); /* 递归遍历左子树 */
        printf("%lc\n", t->data); /* 访问节点 */
        pkt_mid_order(t->rchild); /* 递归遍历右子树 */
    }
}

/* 后序遍历 */
void pkt_after_order(btree_t t)
{
    if(t != NULL)
    {
        pkt_after_order(t->lchild); /* 递归遍历左子树 */
        pkt_after_order(t->rchild); /* 递归遍历右子树 */
        printf("%lc\n", t->data); /* 访问节点 */
    }
}

/* 按层遍历 */
void pkt_level_order(btree_t t)
{
    linkqueue_t q;
    struct message m;
    q = pkt_creat_linkqueue();
    int ret;

    while (t != NULL)
    {
        printf("%lc\n", t->data); /* 访问节点 */
       if(t->lchild != NULL)
       {
           m.data = t->lchild;
           pkt_put_message_linkqueue(q, &m); /* 左子树指针入队 */
       }
       if(t->rchild != NULL)
       {
           m.data = t->rchild;
           pkt_put_message_linkqueue(q, &m); /* 右子树指针入队 */
       }

       if(!(ret = pkt_empty_linkqueue(q)))  /* 队列非空出队，否则结束循环 */
       {
           pkt_take_message_linkqueue(q, &m);
           t = m.data;
       }
       else
       {
           break;
       }
    }
}

void pkt_travel_btree(btree_t t, const char *str, void(*order)(btree_t t))
{
    printf("%s\n", str);
    order(t);
}

int main(int argc, char **argv)
{
    btree_t bt;
    bt = pkt_creat_btree();
#if 0
    printf("prev order:\n");
    pkt_prev_order(bt);

    printf("mid order:\n");
    pkt_mid_order(bt);

    printf("after order:\n");
    pkt_after_order(bt);
#else
    pkt_travel_btree(bt, "prev order", pkt_prev_order);
    pkt_travel_btree(bt, "mid order", pkt_mid_order);
    pkt_travel_btree(bt, "after order", pkt_after_order);
    pkt_travel_btree(bt, "level order", pkt_level_order);
#endif
    return 0;
}