1099. Build A Binary Search Tree (30)

1099. Build A Binary Search Tree (30)

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

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Create : 2018-03-04 16:26:42
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#include <cstdio>
#include <iostream>
#include <algorithm>
#include <cstdlib>
#include <vector>
#include <queue>
using namespace std;
struct Tree{
    Tree *le;
    Tree *ri;
    int data;
};
struct Post{
    int a;
    int b;
};
vector<Post> v;
queue<Tree *> q;
int n;
int pos[105];
int index = 0;
bool key = true;
Tree *Tr = NULL;
Tree* buildTree(Tree *root,int k){
    root = new Tree;
    root->data = k;
    root->le = root->ri = NULL;
    if(v[k].a != -1){
        root->le = buildTree(root->le,v[k].a);
    }
    if(v[k].b != -1){
        root->ri = buildTree(root->ri,v[k].b);
    }
    return root;
}
void inOrder(Tree *root){
    if(root == NULL)return;
    inOrder(root->le);
    root->data = pos[index++];
    inOrder(root->ri);
}
void printLevelOrder(){
    while(!q.empty()){
        Tree *root = q.front();
        if(key == true){
            printf("%d",root->data);
            key = false;
        }else printf(" %d",root->data);
        q.pop();
        if(root->le!= NULL)q.push(root->le);
        if(root->ri!= NULL)q.push(root->ri);
    }

}
int main(){
    scanf("%d",&n);
    Post x;
    for(int i = 0 ; i < n ; i++){
        scanf("%d %d",&x.a,&x.b);
        v.push_back(x);     
    }
    for(int i = 0 ; i < n ; i++){
        scanf("%d",&pos[i]);
    }
    sort(pos,pos+n);
    Tr = buildTree(Tr,0);
    q.push(Tr);
    inOrder(Tr);
    printLevelOrder();
}