目录
1099 Build A Binary Search Tree
1099 Build A Binary Search Tree
题目描述
A Binary Search Tree (BST) is recursively defined as a binary tree which has the following properties:
- The left subtree of a node contains only nodes with keys less than the node's key.
- The right subtree of a node contains only nodes with keys greater than or equal to the node's key.
- Both the left and right subtrees must also be binary search trees.
Given the structure of a binary tree and a sequence of distinct integer keys, there is only one way to fill these keys into the tree so that the resulting tree satisfies the definition of a BST. You are supposed to output the level order traversal sequence of that tree. The sample is illustrated by Figure 1 and 2.
Input Specification:
Each input file contains one test case. For each case, the first line gives a positive integer N (≤100) which is the total number of nodes in the tree. The next N lines each contains the left and the right children of a node in the format left_index right_index, provided that the nodes are numbered from 0 to N−1, and 0 is always the root. If one child is missing, then −1 will represent the NULL child pointer. Finally N distinct integer keys are given in the last line.
Output Specification:
For each test case, print in one line the level order traversal sequence of that tree. All the numbers must be separated by a space, with no extra space at the end of the line.
Sample Input:
9
1 6
2 3
-1 -1
-1 4
5 -1
-1 -1
7 -1
-1 8
-1 -1
73 45 11 58 82 25 67 38 42
Sample Output:
58 25 82 11 38 67 45 73 42解题思路
首先给出每个节点的左子节点和右子节点的编号， 首先我们现根据这些信息生成二叉树
二叉搜索树的中序遍历为数组由小到大的顺序，所以将数组排序后，还原出二叉搜索树
输出层次遍历数据
程序
#include <iostream>
#include <initializer_list>
#include <algorithm>
#include <string>
#include <string.h>
#include <thread>
#include <cmath>
#include <vector>
#include <tuple>
#include <utility>
#include <type_traits>
#include <new>
#include <complex>
#include <queue>
#include <tuple>
#include <map>
using namespace std;
const int maxn = 105;
int n,a[maxn],_index,ans[maxn];
struct Node
{
int left,right,date;
}node[maxn<<1];
void inorder(int pos) //中序遍历还原二叉搜索树
{
if(pos == -1)
return ;
inorder(node[pos].left);
node[pos].date = a[_index++];
inorder(node[pos].right);
}
void bfs()
{
_index = 0;Node tmp;
queue<Node> que;
que.push(node[0]);
while(!que.empty())
{
tmp = que.front();que.pop();
ans[_index++] = tmp.date;
if(tmp.left != -1)
que.push(node[tmp.left]);
if(tmp.right != -1)
que.push(node[tmp.right]);
}
}
int main()
{
scanf("%d",&n);
for(int i = 0 ;i < n;i ++)
scanf("%d%d",&node[i].left,&node[i].right); //直接输入二叉树
for(int i = 0;i < n;i ++)
scanf("%d",a+i);
sort(a,a+n);
inorder(0);
bfs();
for(int i = 0;i < n;i ++)
printf("%d%c",ans[i],i==n-1?'\n':' ');
return 0;
}
参考博客
https://blog.csdn.net/realxuejin/article/details/49591781