PAT A1099. Build A Binary Search Tree (30)

1. Build A Binary Search Tree (30)

时间限制
100 ms
内存限制
65536 kB
代码长度限制
16000 B
判题程序
Standard
作者
CHEN, Yue
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<algorithm>
#include<queue>
using namespace std;
const int maxn=102;
int flag[maxn]={1};
int In[maxn];
int cnt=0;
struct Node{
    int data;
    int l,r;
}node[maxn];
int n;

void LevelOrder(int root){
    int ct=0;
    queue<Node>q;
    q.push(node[root]);
    while(q.size()){
        Node x=q.front();
        printf("%d",x.data);
        ct++;
        if(ct<n)printf(" ");
        q.pop();
        if(x.l!=-1){
            q.push(node[x.l]);
        }
        if(x.r!=-1){
            q.push(node[x.r]);
        }
    }
}
void create(int root){
    if(root==-1)return;
    create(node[root].l);
    node[root].data=In[cnt++];
    create(node[root].r);
}
int main(){

    scanf("%d",&n);
    for(int i=0;i<n;i++){
        scanf("%d %d",&node[i].l,&node[i].r);
        if(node[i].l!=-1)flag[node[i].l]=0;
        if(node[i].r!=-1)flag[node[i].r]=0;
    }
    int root=-1;
    for(int i=0;i<n;i++){
        if(flag[i]==1){
            root=i;
            break;
        }
    }
    for(int i=0;i<n;i++)
        scanf("%d",In+i);
    sort(In,In+n);
    create(root);
    LevelOrder(root);
    return 0;
}