preorder

preorder.cpp

#include<bits/stdc++.h>

using namespace std;

struct Node{
  int root, left, right;
  Node(int root=-1, int left=-1, int right=-1):root(root),left(left),right(right){ }
};

Node tree[11];

void makeEdge(int root, int left=-1, int right=-1){
  tree[root] = Node(root, left, right);
}

void preorder(int root){
  cout << root << ' ';
  if(tree[root].left != -1)preorder(tree[root].left);
  if(tree[root].right != -1)preorder(tree[root].right);
}

int main(){
  //root of tree : 1
  makeEdge(1, 2, 3);
  makeEdge(2, 4);
  makeEdge(3, 5, 6);
  makeEdge(5);
  makeEdge(6, -1, 7);
  makeEdge(4);
  makeEdge(7);
  
  //preorder : root -> left -> right
  preorder(1);
}