CheckBST[1]

Given a binary tree, you are supposed to tell if it is a binary search tree. If the answer is yes, try to find the$K$-th largest key, else try to find the height of the tree.

Format of function:

int CheckBST ( BinTree T, int K );

where BinTree is defined as the following:

typedef struct TNode *BinTree;struct TNode{    int Key;    BinTree Left;    BinTree Right;};

The function CheckBST is supposed to return the K-th largest key ifT is a binary search tree; or if not, return the negative height of T (for example, if the height is $5$, you must return $-5$).

Here the height of a leaf node is defined to be 1. T is not empty and all its keys are positive integers.K is positive and is never more than the total number of nodes in the tree.

Sample program of judge:

#include <stdio.h>#include <stdlib.h>typedef struct TNode *BinTree;struct TNode{    int Key;    BinTree Left;    BinTree Right;};BinTree BuildTree(); /* details omitted */int CheckBST ( BinTree T, int K );int main(){    BinTree T;    int K, out;    T = BuildTree();    scanf("%d", &K);    out = CheckBST(T, K);    if ( out < 0 )        printf("No.  Height = %d\n", -out);    else        printf("Yes.  Key = %d\n", out);    return 0;}/* 你的代码将被嵌在这里 */

Sample Input 1: (for the following tree)

4

Sample Output 1:

Yes.  Key = 5

Sample Input 2: (for the following tree)

3

Sample Output 2:

No.  Height = 3

result:

CheckBST ( BinTree T, int K ){ int situation=1;    BinTree queue[201]; BinTree M; int a[201]; int i; int Front,rear; int height=0; int max; int times=K; int ai=1;    Front=1; rear=1; queue[1]=T; rear++;  if(T->Left==NULL&&T->Right==NULL)  return T->Key; while(Front!=rear) {  if(queue[Front]!=NULL)  {  queue[rear]=queue[Front]->Left;  rear++;  queue[rear]=queue[Front]->Right;  rear++;  }  Front++; } for(i=1;i<rear;i++) {  if(queue[i]==NULL)   continue;  if(queue[i]->Left!=NULL)  {   M=queue[i]->Left;   while(M->Right!=NULL)    M=M->Right;   if(M->Key>queue[i]->Key)   {   situation=2;   break;   }  }  if(queue[i]->Right!=NULL)  {   M=queue[i]->Right;   while(M->Left!=NULL)    M=M->Left;   if(M->Key<queue[i]->Key)   {   situation=2;   break;   }  } } if(situation==2) {  rear--;  while(rear!=0)  {   rear=rear/2;   height++;  }  height=-height;  return height; } else {  Front--;  for(i=1;i<=Front;i++)   if(queue[i]!=NULL)   {   a[ai]=queue[i]->Key;   ai++;   }  max=1;  while(times!=0)  {   for(i=1;i<=ai;i++)   {       if(a[max]<a[i])    max=i;   }   times--;   if(times!=0)    a[max]=0;  }  return a[max]; }}