线索二叉树（中序）

#include <bits/stdc++.h>
using namespace std;
typedef int ElemType;

typedef struct ThrNode{
    ElemType data;
    ThrNode* lson;
    ThrNode* rson;
    int ltag;
    int rtag;
    ThrNode(ElemType data, ThrNode* lson, ThrNode* rson) {
        this->ltag=0;
        this->rtag=0;
        this->data = data;
        this->lson = lson;
        this->rson = rson;
    }
}*ThrTree;

void inThread(ThrTree &p,ThrTree &pre){
    if(p){
        //printf("%d ",p->data);
        inThread(p->lson,pre);
        if(p->ltag){
            p->ltag=1;
            p->lson=pre;
        }
        if(pre&&!pre->rtag){
            pre->rtag=1;
            pre->rson=p;
        }
        pre=p;
        inThread(p->rson,pre);
    }
}

void dfs(ThrTree T){
    if(T){
        printf("%d ",T->data);
        dfs(T->rson);
    }
}


int main(){
    ThrNode* v7 = new ThrNode(7, NULL, NULL);
    ThrNode* v1 = new ThrNode(1, NULL, NULL);
    ThrNode* v3 = new ThrNode(3, NULL, NULL);
    ThrNode* v2 = new ThrNode(2, v1, v3);
    ThrNode* v5 = new ThrNode(5, NULL, NULL);
    ThrNode* v6 = new ThrNode(6, v5, v7);
    ThrNode* v4 = new ThrNode(4, v2, v6);

    ThrTree T=v4,pre=NULL;
    ThrTree p=T;
    p=p->lson;
    printf("%d
",p->data);
    inThread(T,pre);
    p=T;
    p=p->lson;
    printf("%d
",p->data);
    p=p->lson;
    //dfs(p);
    //printf("%d",get_kth_number(T,4));
}