6_41_递归求出二叉树先序遍历第k个节点的元素的值

#include<stdio.h>
#include<stdlib.h>
#include<malloc.h>
typedef struct node
{
    int data;
    struct node*lchild,*rchild;
}tnode,*tree;
tree creat()
{
    int x;
    tree t;
    scanf("%d",&x);
    if(x==0)t=NULL;
    else
    {
        t=(tnode*)malloc(sizeof(tnode));
        t->data=x;
        t->lchild=creat();
        t->rchild=creat();
    }
    return t;
}
int TreeNum(tree t,int *k)
{
    if(t)
    {
        (*k)--;if(*k==0)return t->data;
        if(*k!=0)return TreeNum(t->lchild,k);
        if(*k!=0)return TreeNum(t->rchild,k);
    }
    return -1;
}
int main()
{
    int n;
    tree t=creat();
    printf("input a number:	
");
    scanf("%d",&n);
    printf("%d
",TreeNum(t,&n));
}

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