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.
figBST.jpg
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
给定一个二叉树的形状，将给定的中序遍历顺序的二叉树插入，并输出层序遍历的结果
充分利用数组形式储存的二叉树的下标，利用一个游标指向输入的中序遍历顺序的头部，然后递归填充二叉树。
#include<bits/stdc++.h>
using namespace std;
struct TreeNode{
int val, left = -1, right = -1;
};
void inorder(vector<TreeNode>& tree, vector<int>& A, int root, int& index){
if (root==-1) return;
inorder(tree, A,tree[root].left, index);
tree[root].val = A[index++];
inorder(tree, A,tree[root].right, index);
}
int main()
{
int n, a, b,index=0;
cin >> n;
vector<TreeNode>tree(n);
for (int i = 0; i < n; i++)
cin >> tree[i].left >> tree[i].right;
vector<int>A(n),re;
for (int i = 0; i < n; i++)
cin >> A[i];
sort(A.begin(), A.end());
inorder(tree, A, 0, index);
queue<int>que;
que.push(0);
while (!que.empty()){
int num = que.size();
for(;num--;que.pop()){
auto top = que.front();
re.push_back(tree[top].val);
if(tree[top].left!=-1)
que.push(tree[top].left);
if (tree[top].right!= -1)
que.push(tree[top].right);
}
}
for (int i = 0; i < re.size(); i++)
cout<<(i==0?"":" ")<<re[i];
return 0;
}