Question

The Problem Complete the printFromButtom function that accepts a BST TreeNode and returns the nodes' value from left to right, level by level from leaf to root. This function will return vector<vector int which similar to a 2-D array. Function std: reverse (myvector.begin myVector en might be helpful. Definition for a binary tree node: struct TreeNode int val TreeNode *left; TreeNode right Examples Example 1 Sample Binary Search Tree: 9 20 15 7 Result: [15,7], 19,20] [3]

Coding Language: C++

Function Header: vector<vector<int>> printFromButtom(TreeNode* root) {}

Definition for a binary tree node:

struct TreeNode {
int val;
TreeNode *left;
TreeNode *right;
};

Answer 1

#include <iostream>
#include <iostream>
#include <stack>
#include <queue>
#include <algorithm>
using namespace std;
struct TreeNode
{
    int val;
    struct TreeNode* left;
    struct TreeNode* right;
};
using namespace std;
vector< vector<int> > printFromBottom(TreeNode* root)
{
    vector< vector<int> > ans;
    queue <TreeNode *> Q;
    Q.push(NULL);
    Q.push(root);
vector<int> temp;
    while (Q.empty() == false)
    {
        root = Q.front();
        Q.pop();
        if(root==NULL){
         std::reverse(temp.begin(), temp.end());
            ans.push_back(temp);
            if(Q.empty() == true)
                break;
            Q.push(NULL);
            temp.clear();
      
        }else{
          temp.push_back(root->val);
        if (root->right)
            Q.push(root->right);

        if (root->left)
            Q.push(root->left);
        }
      
    }

    std::reverse(ans.begin(), ans.end());
        for(int i=0;i<ans.size();++i){
            cout << endl;
            for(int j=0;j<ans[i].size();++j)
                cout << ans[i][j] << " ";
        }
      
    return ans;
}
TreeNode* newNode(int data)
{
    TreeNode* temp = new TreeNode;
    temp->val = data;
    temp->left = NULL;
    temp->right = NULL;

    return (temp);
}

/* Driver program to test above functions*/
int main()
{
    struct TreeNode *root = newNode(3);
    root->left        = newNode(9);
    root->right       = newNode(20);
    root->right->left = newNode(15);
    root->right->right = newNode(7);

    cout << "Print from Bottom \n";
    printFromBottom(root);

    return 0;
}

==================================================================================
See output

日ロ+ 《 * New Project-201 70310 BAコroot Compile ! | Execute i l > Share Code main.cppx struct TreeNode *root -newNode(3); root->left root->right root->right->leftnewNode (15); root->right->rightnewNode(7); main.cpp newNode(9); - newNode(20); 67 68 69 70 71 72 73 74 75 76 cout << "Print from Bottom In"; printFromBottom(root); return 0; Default Term + Browser sh-4.2$ g++ -o main *.cpp sh-4.2$ main Print from Bottom 15 7 9 20 sh-4.2$

Thanks, let me know if there is any concern.