Suppose that all the keys in a binary tree are distinct positive integers. Given the postorder and inorder traversal sequences, you are supposed to output the level order traversal sequence of the corresponding binary tree.
Input Specification:
Each input file contains one test case. For each case, the first line gives a positive integer N (<=30), the total number of nodes in the binary tree. The second line gives the postorder sequence and the third line gives the inorder sequence. All the numbers in a line are separated by a space.
Output Specification:
For each test case, print in one line the level order traversal sequence of the corresponding binary tree. All the numbers in a line must be separated by exactly one space, and there must be no extra space at the end of the line.
#include <stdio.h>
#include <stdlib.h>
#include <queue>
using namespace std;
typedef struct Node
{
int id;
struct Node *left,*right;
}Node;
Node * Creat(int * post,int ps,int pe,int * in,int is,int ie);
void BFS (Node * root);
int n;
int main ()
{
int i;
scanf("%d",&n);
int *post=new int[n];
int *in=new int[n];
for( i=0;i<n;i++)
{
scanf("%d",post+i);
}
for( i=0;i<n;i++)
{
scanf("%d",in+i);
}
Node *root=Creat(post,0,n-1,in,0,n-1);
BFS(root);
printf("\n");
system("pause");
return 0;
}
void BFS (Node * root)
{
queue<Node *>q;
q.push(root);
Node *temp=new Node;
int count=0;
while( !q.empty())
{
temp=q.front();
q.pop();//出队
printf("%d",temp->id);
count++;
if(count<n) printf(" ");
if(temp->left) q.push(temp->left);
if(temp->right) q.push(temp->right);
}
}
Node * Creat(int * post,int ps,int pe,int * in,int is,int ie)
{
if(ps>pe) return NULL;
Node * root=new Node;
root->id=post[pe];
int i;
for( i=is;i<=ie;i++) if(in[i]==root->id) break;
int num=i-is;
root->left=Creat(post,ps,ps+num-1,in,is,i-1);
root->right=Creat(post,ps+num,pe-1,in,i+1,ie);
return root;
}
