数据结构---判断一棵树是否是二叉搜索树

数据结构—判断一棵树是否是二叉搜索树

代码：

#pragma once
#define N 100
#define elemType BTree*
#include<stdlib.h>
typedef struct BTree {int data;struct BTree *lchild, *rchild;
}BTree;
typedef struct dQueue {elemType data;struct dQueue* next;
}dQueue;
typedef struct queue {dQueue *front, *rear;
}queue;
bool initQueue(queue &Queue) {//初始化队列//Queue.front = new dQueue;Queue.front = Queue.rear = (dQueue*)malloc(sizeof(dQueue));if (!Queue.front) {return false;}Queue.front->next = NULL;//头结点return true;
}
elemType getQueueTopElem(queue &Queue) {//获取队列队头的元素elemType u=NULL ;if (Queue.front != Queue.rear) {dQueue* p = Queue.front->next;u = p->data;}return u;
}
bool enQueue(queue &Queue, elemType e) {//入队dQueue* p = Queue.rear;dQueue* s = (dQueue*)malloc(sizeof(dQueue));s->data = e;s->next = NULL;p->next = s;Queue.rear = s;return true;
}
bool deQueue(queue &Queue, elemType &e) {//出队if (Queue.front == Queue.rear) {return false;//空队}dQueue* p = Queue.front->next;e = p->data;Queue.front->next = p->next;if (p == Queue.rear) {//队尾只有一个元素的时候Queue.rear = Queue.front;}delete p;return true;
}
bool emptyQueue(queue Queue) {//队列为空的判断if (Queue.front == Queue.rear) {return true;}return false;
}

#include <stdio.h>
#include <stdlib.h>
//#include "BTree.h"
#include"queue.h"
int preElem = -1;
void createBSTTree(BTree* & T, int data) {//创建二叉排序树BTree *p = NULL;if (!T) {p = (BTree*)malloc(sizeof(BTree));p->data = data;p->lchild = p->rchild = NULL;T = p;return;}if (data < T->data) {//左子树插入createBSTTree(T->lchild, data);}else {//右子树插入createBSTTree(T->rchild, data);}
}
int isBST(BTree* bTree) {//必须满足严格的左子树结点的值小于跟结点的值，右节点的值大于根节点的值int b1, b2;//中序遍历+递归返回值影响if (bTree == NULL) {//小条件退出return 1;}else {b1 = isBST(bTree->lchild);if (b1 == 0 || preElem >= bTree->data) {return 0;}preElem = bTree->data;b2 = isBST(bTree->rchild);return b2;}
}
int isBST2(BTree* btree) {//非递归queue q;initQueue(q);enQueue(q, btree);while (!emptyQueue(q)) {BTree* temp;deQueue(q, temp);if (temp&&temp->lchild) {if(temp->lchild->data >= temp->data)return 0;elseenQueue(q, temp->lchild);	}if (temp&&temp->rchild) {if (temp->rchild->data < temp->data)return 0;elseenQueue(q, temp->rchild);}}return 1;
}
void midTraverseTree(BTree*  BSTTree) {//中序遍历二叉排序树if (BSTTree) {midTraverseTree(BSTTree->lchild);printf("%d ", BSTTree->data);midTraverseTree(BSTTree->rchild);}
}
int main() {BTree* T = NULL;//一定要初始化为空树int count, data;printf("开始构造二叉排序树:\n输入二叉排序树结点的数目:");scanf_s("%d", &count);while (count--) {//构造二叉排序树printf("输入二叉树的第%d个结点:", count + 1);scanf_s("%d", &data);createBSTTree(T, data);}printf("中序遍历二叉树\n");midTraverseTree(T);//中序遍历二叉排序树printf("\n方法一判断是否是二叉排序树\n");if (isBST(T)) {printf("\n是二叉排序树\n");}else {printf("\n不是二叉排序树\n");}printf("\n方法二判断是否是二叉排序树\n");if (isBST2(T)) {printf("\n是二叉排序树\n");}else {printf("\n不是二叉排序树\n");}printf("\n");system("pause");return 0;
}