二叉树的建立和遍历

#include<bits/stdc++.h>
#define INF 0x3f3f3f3f3f3f3f3f
#define mod 1000000007
#define IOS ios::sync_with_stdio(false)
#define endl '\n'
using namespace std;
typedef long long ll;
const int maxn = 1e5 + 10;
typedef struct Node {
  int data;
  Node* left, * right;
}node;
void preorder(Node *node) {//前序遍历
  if (node != NULL) {
    printf("%d\n", node->data);
    preorder(node->left);
    preorder(node->right);
  }
}
void inorder(Node* node) {//中序遍历
  if (node != NULL) {
    inorder(node->left);
    printf("%d\n", node->data);
    inorder(node->right);
  }
}
void postorder(Node* node) {//后序遍历
  if (node != NULL) {
    postorder(node->left);
    postorder(node->right);
    printf("%d\n", node->data);
  }
}
int main() {
  node n1, n2, n3, n4, n5, n6, n7;
  //暴力建树//
  n1.data = 1;
  n2.data = 2;
  n3.data = 3;
  n4.data = 4;
  n5.data = 5;
  n6.data = 6;
  n7.data = 7;
  n1.left = &n2;
  n1.right = &n3;
  n2.right = &n5;
  n2.left = &n4;
  n3.left = &n6;
  n3.right = &n7;
  n4.left = NULL;
  n4.right = NULL;
  n5.left = NULL;
  n5.right = NULL;
  n6.right = NULL;
  n6.left = NULL;
  n7.right = NULL;
  n7.left = NULL;
  preorder(&n1);
  printf("\n");
  inorder(&n1);
  printf("\n");
  postorder(&n1);
}