1099. 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
  

平衡二叉树。每次找到中间节点。

 1 #include<cstdio>
 2 #include<stack>
 3 #include<algorithm>
 4 #include<iostream>
 5 #include<stack>
 6 #include<queue>
 7 #include<map>
 8 using namespace std;
 9 struct node{
10     int l,r,v;
11 };
12 node tree[105];
13 int line[105];
14 int calnum(int num){
15     if(num==-1){
16         return 0;
17     }
18     return calnum(tree[num].l)+calnum(tree[num].r)+1;
19     }
20 void BuildAVL(int mid,int *line){
21     if(mid==-1){
22         return ;
23     }
24     int count=calnum(tree[mid].l);//统计左子树
25
26     //cout<<count<<endl;
27
28     tree[mid].v=line[count];
29     BuildAVL(tree[mid].l,line);
30     BuildAVL(tree[mid].r,line+count+1);
31 }
32 int main(){
33     //freopen("D:\\INPUT.txt","r",stdin);
34     int n;
35     scanf("%d",&n);
36     int i;
37     for(i=0;i<n;i++){
38         scanf("%d %d",&tree[i].l,&tree[i].r);
39     }
40     for(i=0;i<n;i++){
41         scanf("%d",&line[i]);
42     }
43     sort(line,line+n);
44
45     /*for(i=0;i<n;i++){
46         cout<<i<<" "<<line[i]<<endl;
47     }*/
48
49     BuildAVL(0,line);
50
51     //cout<<":"<<"  "<<tree[0].v<<endl;
52
53     queue<int> q;
54     int cur;
55     q.push(0);
56     printf("%d",tree[0].v);
57     while(!q.empty()){
58         cur=q.front();
59         q.pop();
60         //cout<<"cur:  "<<cur<<endl;
61
62         if(tree[cur].l!=-1){
63             q.push(tree[cur].l);
64             printf(" %d",tree[tree[cur].l].v);
65         }
66         if(tree[cur].r!=-1){
67             q.push(tree[cur].r);
68             printf(" %d",tree[tree[cur].r].v);
69         }
70     }
71     printf("\n");
72     return 0;
73 }