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

 

#include<cstdio>
#include<queue>
#include<algorithm>
using namespace std;
const int maxn = 110;
struct Node{
    int data;
    int lchild,rchild;
}node[maxn];
int n,in[maxn],num = 0;

void inorder(int root){
    if(root == -1) return;
    inorder(node[root].lchild);
    node[root].data = in[num++];
    inorder(node[root].rchild);
}

void BFS(int root){
    queue<int> Q;
    Q.push(root);
    int num = 0;
    while(!Q.empty()){
        int Now = Q.front();
        Q.pop();
        printf("%d",node[Now].data);
        num++;
        if(num < n) printf(" ");
        if(node[Now].lchild != -1) Q.push(node[Now].lchild);
        if(node[Now].rchild != -1) Q.push(node[Now].rchild);
    }
}

int main(){
    int lchild,rchild;
    scanf("%d",&n);
    for(int i = 0; i < n; i++){
        scanf("%d%d",&lchild,&rchild);
        node[i].lchild = lchild;
        node[i].rchild = rchild;
    }
    for(int i = 0; i < n; i++){
        scanf("%d",&in[i]);
    }
    sort(in,in+n);
    inorder(0);
    BFS(0);
    return 0;
}