Shopee笔试题

Shopee笔试

遍历二叉树

#include <iostream>

using namespace std;
struct Node{
  int val;
  Node* left;
  Node* right;
};		//定义树的结点

void preorder(Node* node){  //先序遍历
    if(node != NULL){
        cout << node->val << " ";
        preorder(node->left);
        preorder(node->right);
    }
}
void midorder(Node* node){
    if(node!=NULL){
        midorder(node->left);
        cout << node->val << " ";
        midorder(node->right);
    }
}

void lastorder(Node* node){
    if(node!=NULL){
        lastorder(node->left);
        lastorder(node->right);
        cout << node->val << " ";
    }
}

int main(){
  //生成树方法1：暴力生成树的结点,然后依次使用指针连接起来
  Node* a = new Node();            //a是结点1#的指针
  Node* b = new Node();            //b是结点2#的指针
  Node* c = new Node();
  Node* d = new Node();
  a->val = 5;
  b->val = 6;
  c->val = 7;
  d->val = 8;

  a->left =b;
  a->right=c;
  b->left =d;
  b->right= NULL;
  c->left = NULL;
  c->right= NULL;
  d->left = NULL;
  d->right= NULL;
    // 生成树方法2：   BST（二叉搜索树）动态建立树的方法


  preorder(a);
  cout << endl;
  midorder(a);
  cout << endl;
  lastorder(a);
  cout << endl;
  return 0;
}

生成(建立)二叉树之二叉搜索树

#include<iostream>

using namespace std;
struct Node{
  int val;
  Node* left;
  Node* right;
};

struct Tree{
  	Node* root; 
};	//这样可以把整个结点打包起来，一棵树只要保存根节点就OK

void insert(Tree* tree,int num){	//将结点插入到树中
  	//创造新结点
  	Node* p = new Node();
  	p->val  = num;
    p->left = NULL;
    p->right= NULL;
  
    if(tree->root == NULL){
      tree->root = p;	   //新创造的节点插入到树上
    }else{		           //已经有根了
      
      Node* temp = tree->root;
      while(temp!=NULL){
        if(num < temp->val){	//两种情况，一种是左边是空的；另一种是左边不为空
          if(temp->left == NULL){
             temp->left = node;
            return 0;
          }else{
            temp = temp->left;
          }
        }else{
          if(num < temp->val){   //还是两种情况，一种是右边是空直接插入；另一种是右边不是空继续右下移
            if(temp->right == NULL){
              temp->right = node;
              return ;
            }else{
              temp = temp -> right;
            }
            
          }
        }
      }
      
    }
}

int main(){
  Tree tree;
  tree.root = NULL;
  int nums[7] = {3,5,2,6,8,1,4}
  for(int i=0;i<7;i++){
    insert(&tree,nums[i]);
  }
  
  return 0;
}