1043. Is It a Binary Search Tree (25)

题目连接：https://www.patest.cn/contests/pat-a-practise/1043

今天难道是我状态不佳？……

思路很清晰，以两种规则建树，分别得到其前序数组，和原始数组进行比较，若有相等的则将该树后序遍历输出。

遗忘和不熟悉的知识点：BST（搜索树）及相关如插入操作等；vector变量之间可以进行比较。

#include<stdio.h>
#include<vector>
#include<stdlib.h>
#define MAXN 1005
using namespace std;
typedef struct TNode{
    int Data;
    struct TNode*Left;
    struct TNode*Right;
}BT;
int N;

BT* Insert1(BT* T1,int x)
{
    if (!T1)
    {
        T1=(BT*)malloc(sizeof(struct TNode));
        T1->Data=x;
        T1->Left=T1->Right=NULL;
    }
    else
    {
        if (x>=T1->Data)T1->Right=Insert1(T1->Right,x);
        else if (x<T1->Data)T1->Left=Insert1(T1->Left,x);
    }
    return T1;
}

BT* Insert2(BT* T2,int x)
{
    if (!T2)
    {
        T2=(BT*)malloc(sizeof(struct TNode));
        T2->Data=x;
        T2->Left=T2->Right=NULL;
    }
    else
    {
        if (x>=T2->Data)T2->Left=Insert2(T2->Left,x);
        else if (x<T2->Data)T2->Right=Insert2(T2->Right,x);
    }
    return T2;
}

void Perorder(BT*T,vector<int>&v)
{
    if (T)
    {
        v.push_back(T->Data);
        Perorder(T->Left,v);
        Perorder(T->Right,v);
    }
}

void Postorder(BT*T,vector<int>&v)
{
    if (T)
    {
        Postorder(T->Left,v);
        Postorder(T->Right,v);
        v.push_back(T->Data);
        //printf("%d ",T->Data);
    }
}

void Out(BT *T,vector<int>&v)
{
    Postorder(T,v);
    int i;
    for (i=0;i<N;i++)
    {
    if (i==0)printf("%d",v[i]);
    else printf(" %d",v[i]);
    }
}
int main()
{
    int i,v;
    vector<int>v1,v2,v3,ans;
    scanf("%d",&N);
    for (i=0;i<N;i++){scanf("%d",&v);v1.push_back(v);}
    BT*T1,*T2;
    T1=T2=NULL;

    for (i=0;i<N;i++)
    {
        T1=Insert1(T1,v1[i]);
        T2=Insert2(T2,v1[i]);
    }
    Perorder(T1,v2);
    Perorder(T2,v3);
    if (v1!=v2 &&v1!=v3)
    {
        printf("NO");
        return 0;
    }
    else
    {
        printf("YES
");
        if (v1==v2)Out(T1,ans);
        else if (v1==v3)Out(T2,ans);
    }
    return 0;
}