Given a Binary tree, the task is to print its all level in sorted order
Examples:
Input : 7
/ \
6 5
/ \ / \
4 3 2 1
Output :
7
5 6
1 2 3 4
Input : 7
/ \
16 1
/ \
4 13
Output :
7
1 16
4 13
Here we can use two Priority queue for print in sorted order. We create an empty queue q and two priority queues, current_level and next_level. We use NULL as a separator between two levels. Whenever we encounter NULL in normal level order traversal, we swap current_level and next_level.
// CPP program to print levels in sorted order.#include <iostream>#include <queue>#include <vector>using namespace std; // A Binary Tree Nodestruct Node { int data; struct Node *left, *right;}; // Iterative method to find height of Binary Treevoid printLevelOrder(Node* root){ // Base Case if (root == NULL) return; // Create an empty queue for level order traversal queue<Node*> q; // A priority queue (or min heap) of integers for // to store all elements of current level. priority_queue<int, vector<int>, greater<int> > current_level; // A priority queue (or min heap) of integers for // to store all elements of next level. priority_queue<int, vector<int>, greater<int> > next_level; // push the root for traverse all next level nodes q.push(root); // for go level by level q.push(NULL); // push the first node data in previous_level queue current_level.push(root->data); while (q.empty() == false) { // Get top of priority queue int data = current_level.top(); // Get top of queue Node* node = q.front(); // if node == NULL (Means this is boundary // between two levels), swap current_level // next_level priority queues. if (node == NULL) { q.pop(); // here queue is empty represent // no element in the actual // queue if (q.empty()) break; q.push(NULL); cout << "\n"; // swap next_level to current_level level // for print in sorted order current_level.swap(next_level); continue; } // print the current_level data cout << data << " "; q.pop(); current_level.pop(); /* Enqueue left child */ if (node->left != NULL) { q.push(node->left); // Enqueue left child in next_level queue next_level.push(node->left->data); } /*Enqueue right child */ if (node->right != NULL) { q.push(node->right); // Enqueue right child in next_level queue next_level.push(node->right->data); } }} // Utility function to create a new tree nodeNode* newNode(int data){ Node* temp = new Node; temp->data = data; temp->left = temp->right = NULL; return temp;} // Driver program to test above functionsint main(){ // Let us create binary tree shown in above diagram Node* root = newNode(7); root->left = newNode(6); root->right = newNode(5); root->left->left = newNode(4); root->left->right = newNode(3); root->right->left = newNode(2); root->right->right = newNode(1); /* 7 / \ 6 5 / \ / \ 4 3 2 1 */ cout << "Level Order traversal of binary tree is \n"; printLevelOrder(root); return 0;} |
Level Order traversal of binary tree is 7 5 6 1 2 3 4
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