pat 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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• 
  
  #include<iostream>
  #include<algorithm>
  #include<queue>
  
  
  using namespace std;
  
  
  class node{
  public:int l,r,d;
  };
  bool cmp(int a,int b){
  return a<b;
  }
  
  
  int n,x=0;
  node tree[101];
  int arr[101];
  
  
  int med_order(int h){
  if(h==-1) return 0;
  med_order(tree[h].l);
  tree[h].d=arr[x++];
  med_order(tree[h].r);
  return 0;
  }
  
  
  int main(){
  
  
  int n;
  cin>>n;
  for(int i=0;i<n;i++)
  {
  cin>>tree[i].l>>tree[i].r;
  }
  
  
  for(int i=0;i<n;i++)
  cin>>arr[i];
  
  
  sort(arr,arr+n,cmp);
  
  
  med_order(0);
  
  
  queue<int> q;
  int t;
  q.push(0);
  int tt=0;
  while(!q.empty())
  {
  t=q.front();
  q.pop();
  if(tt==0) cout<<tree[t].d,tt++;
  else cout<<" "<<tree[t].d;
  if(tree[t].l!=-1) q.push(tree[t].l);
  if(tree[t].r!=-1) q.push(tree[t].r);
  
  }
  }