PAT (Advanced Level) 1099. Build A Binary Search Tree (30) 中序遍历往BST中填数据

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
/*2015.8.1cyq*/
#include <iostream>
#include <vector>
#include <algorithm>
#include <queue>
#include <fstream>
using namespace std;

//ifstream fin("case1.txt");
//#define cin fin

struct node{
int val;
int left;
int right;
};
//中序遍历填入数据
void inOrder(vector<node> &tree,int root,const vector<int> &a,int &index){
if(root!=-1){
inOrder(tree,tree[root].left,a,index);
tree[root].val=a[index++];
inOrder(tree,tree[root].right,a,index);
}
}
int main(){
int N;
cin>>N;
vector<node> tree(N);
for(int i=0;i<N;i++){
cin>>tree[i].left;
cin>>tree[i].right;
}

vector<int> a(N);
for(int i=0;i<N;i++)
cin>>a[i];

sort(a.begin(),a.end());//对数组排序
int index=0;
inOrder(tree,0,a,index);//中根遍历填入数据

vector<int> result;
queue<node> cur;
cur.push(tree[0]);
while(!cur.empty()){//层序遍历，BFS
node tmp=cur.front();
cur.pop();
result.push_back(tmp.val);
if(tmp.left!=-1)
cur.push(tree[tmp.left]);
if(tmp.right!=-1)
cur.push(tree[tmp.right]);
}
cout<<result[0];
for(int i=1;i<N;i++)
cout<<" "<<result[i];
return 0;
}