递归法（非递归法）遍历二叉树

 

- 2.4 用递归法（非递归法）实现先序遍历、中序遍历和后序遍历函数，要求遍历时能执行一定的操作，且该操作可由遍历函数的调用者来设置。

 

提示：可将结点定义成如下结构体：

#define TREE_TYPE int

 

typedef struct TREE_NODE{

       TREE_TYPE value;

       struct TREE_NODE *left;                   左结点指针

       struct TREE_NODE *right;                 右结点指针

}TreeNode;

 

先序遍历与创建二叉树；递归法

#include "tree.h"

#include <stdio.h>

 

btree *creat_bintree(btree *t)

{ char ch;

 

    printf("/n enter ch in preorder, 1 for no child:");

    ch=getchar();

    getchar();

 

    if ( ch=='1')

    {

        printf("The tree has only head node!/n");

        t = NULL;

    }

    else

    {

        t = (btree *)malloc(sizeof(btree));

        t->data=ch;

        t->lchild = (btree *)creat_bintree( t->lchild );

        t->rchild = (btree *)creat_bintree( t->rchild );

    }

    return(t);

}

非递归实现；

#include "tree.h"

 

void preorder_norecu(btree *t)

{

    btree *s[20], *p =t; //p is the current node

    int top = 0;

    while(p || top) // p isn't NULL

    if(p)

    {

        visit(p); //visit the cur node

        ++top;

        s[top] = p; //save cur node to s[top];

        p=p->lchild; //p is directed to lchild node;

    }

    else   //p is NULL

    {

        p=s[top]; //let p direct to s[top];

        --top; //decrease the top;

        p=p->rchild; //test rchild is NULL or not?

    }

}

中序遍历;

#include "tree.h"

 

void in_tree(btree *t)

{

    if(t == NULL)

        return -1;

    else

    {

        in_tree(t->lchild);

        putchar(t->data);

        in_tree(t->rchild);

    }

}

非递归实现：

#include "tree.h"

 

void in_norecursive(btree *t)

{

    btree * s[MAX],*p=t; //p is directed to head node;

    int top=0;

    while(p || top !== NULL) //p isn't NULL

    if(p)  

    {

        top++; //top add

        s[top]=p;   //save current node;

        p=p->lchild; //let p directed to lchild;

    }

    else

    {

        p=s[top]; //p is NULL,let p directed to s[top];

        --top; //push(s)

        visit(p); //visit the p node;

        p=p->rchild; //direct the right child;

    }

}

后续遍历同上；