A1020 Tree Traversals (25 分)

#include <bits/stdc++.h>
using namespace std;

struct node{
  int date;
  node* lchild;
  node* rchild;
};

int post[30];
int in[30];
int n;
node* create(int postL, int postR, int inL, int inR){
  if(postL >postR){
    return NULL;
  }
  node* root = new node;
  root->date = post[postR];
  int k;
  for(k = inL; k < inR; k++){
    if(in[k] == post[postR]){
      break;
    }
  }
  int num = inR - k;
  root->lchild = create(postL, postR-num-1, inL, k-1);
  root->rchild = create(postR-num, postR-1, k+1, inR);
  return root;
} 


void levelOrder(node* tree){
  queue<node*> q;
  q.push(tree);
  int num = 0;
  while(!q.empty()){
    num++;
    node* root = q.front();
    q.pop();
    cout << root->date;
    if(num < n) cout << " ";
    if(root->lchild!=NULL) q.push(root->lchild);
    if(root->rchild!=NULL) q.push(root->rchild);  
  }
}

int main(int argc, char** argv) {
  

  cin >> n;
  for(int i = 0; i < n; i++){
    cin >> post[i];
  }
  for(int i = 0; i < n; i++){
    cin >> in[i];
  }
  
  node* root = create(0,n-1, 0, n-1);
  levelOrder(root);
  return 0;
}