04-树7. Search in a Binary Search Tree (25)

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To search a key in a binary search tree, we start from the root and move all the way down, choosing branches accordingto the comparison results of the keys. The searching path corresponds to a sequence of keys. For example, following {1, 4, 2, 3} we can find 3 from a binary search tree with 1 as its root. But {2, 4, 1, 3} is not such a path since 1 is in theright subtree of the root 2, which breaks the rule for a binary search tree. Now given a sequence of keys, you aresupposed to tell whether or not it indeed correspnds to a searching path in a binary search tree.

Input Specification:

Each input file contains one test case. For each case, the first line gives two positive integers N and M (<=100) which are the total number of sequences, and the size of each sequence, respectively. Then N lines follow, each gives a sequence of keys. It is assumed that the keys are numbered from 1 to M.

Output Specification:

For each sequence, print in a line "YES" if the sequence does correspnd to a searching path in a binary search tree, or "NO" if not.

Sample Input:

3 41 4 2 32 4 1 33 2 4 1

Sample Output:

YESNONO

提交代码

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能说，自己没有看懂题目。。。。

其实，这个题目的意思就是说，给出的序列是不是一个搜索序列。

比如，你搜索的时候，肯定是一直在一颗子树上进行的，不可能在两棵树之间进行跳跃。

编程思路是，读取数据之后，将其插入树中，如果，不在子树的子树上进行插入，就是false的。

同时，在编写插入数据的时候，需要将树的root的地址传入，因为自己想通过递归，递归出来false还是true。

传入地址后，这样会改变传入的root的值，这点在刚刚开始的时候，一直没有改变，通过单步调试可以看出没有什么变化的，所以需要。

同时，*运算符和->运算符的优先级的大小，需要加上一个括号。

代码如下。

#include <iostream>#include <stdlib.h>using namespace std;/* run this program using the console pauser or add your own getch, system("pause") or input loop */typedef struct BinNode{int data;BinNode *l;BinNode *r;}*BinTree;bool Insert(BinTree *bt, int d){if(!*bt){*bt=(BinTree)malloc(sizeof(struct BinNode));(*bt)->l=(*bt)->r=NULL;(*bt)->data=d;}else{if(d<(*bt)->data && (*bt)->r==NULL){if(!Insert(&((*bt)->l),d))return false;}else if(d>(*bt)->data&& (*bt)->l==NULL){if(!Insert(&((*bt)->r),d))return false;}else{return false;}}return true;}int main(int argc, char** argv) {int N=0, M=0;cin>>N>>M;for(int i=0; i<N; i++){int j=0;BinTree root=NULL;for(j=0; j<M; j++){int tmp=0;cin>>tmp;if(!Insert(&root,tmp)){printf("NO\n");break;}}if(j==M)    printf("YES\n");}return 0;}

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