PAT A1099. 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:

91 62 3-1 -1-1 45 -1-1 -17 -1-1 8-1 -173 45 11 58 82 25 67 38 42

Sample Output:

58 25 82 11 38 67 45 73 42

#include <cstdio>#include <iostream>#include <algorithm>#include <cstring>#include <stack>#include <queue>#include <vector>using namespace std;const int Max = 110;int n;struct Node{int data;int lchild;int rchild;int parent;}S[Max];int D[Max],k=0,A[Max];void Inorder(int i){if(S[i].lchild!=-1)Inorder(S[i].lchild);S[i].data=D[k++];if(S[i].rchild!=-1)Inorder(S[i].rchild);}int main(){scanf("%d",&n);int temp,ans;for(int i=0;i<n;i++){scanf("%d%d",&temp,&ans);S[i].lchild=temp;S[temp].parent=i;S[i].rchild=ans;S[ans].parent=i;}for(int i=0;i<n;i++){scanf("%d",&D[i]);}sort(D,D+n);Inorder(0);queue<int >q;while(!q.empty()){q.pop();}q.push(0);while(!q.empty()){temp=q.front();q.pop();printf("%d",S[temp].data);if(S[temp].lchild!=-1)  q.push(S[temp].lchild);    if(S[temp].rchild!=-1)  q.push(S[temp].rchild);if(!q.empty())  printf(" ");}system("pause");return 0;}