order traversal in spiral form

ordertraversalinspiral.cpp

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+// C++ program for recursive level
+// order traversal in spiral form
+#include <bits/stdc++.h>
+using namespace std;
+
+// A binary tree node has data,
+// pointer to left child and a
+// pointer to right child
+struct node {
+	int data;
+	struct node* left;
+	struct node* right;
+};
+
+// Function prototypes
+void printGivenLevel(struct node* root, int level, int ltr);
+int height(struct node* node);
+struct node* newNode(int data);
+
+// Function to print spiral traversal of a tree
+void printSpiral(struct node* root)
+{
+	int h = height(root);
+	int i;
+
+	// ltr -> Left to Right. If this variable
+	// is set,then the given level is traversed
+	// from left to right.
+	bool ltr = false;
+	for (i = 1; i <= h; i++) {
+		printGivenLevel(root, i, ltr);
+
+		// Revert ltr to traverse next
+		// level in opposite order
+		ltr = !ltr;
+	}
+}
+
+// Print nodes at a given level
+void printGivenLevel(struct node* root, int level, int ltr)
+{
+	if (root == NULL)
+		return;
+	if (level == 1)
+		cout << root->data << " ";
+
+	else if (level > 1) {
+		if (ltr) {
+			printGivenLevel(root->left, level - 1, ltr);
+			printGivenLevel(root->right, level - 1, ltr);
+		}
+		else {
+			printGivenLevel(root->right, level - 1, ltr);
+			printGivenLevel(root->left, level - 1, ltr);
+		}
+	}
+}
+
+// Compute the "height" of a tree -- the number of
+// nodes along the longest path from the root node
+// down to the farthest leaf node.
+int height(struct node* node)
+{
+	if (node == NULL)
+		return 0;
+	else {
+
+		// Compute the height of each subtree
+		int lheight = height(node->left);
+		int rheight = height(node->right);
+
+		// Use the larger one
+		if (lheight > rheight)
+			return (lheight + 1);
+		else
+			return (rheight + 1);
+	}
+}
+
+// Helper function that allocates a new
+// node with the given data and NULL left
+// and right pointers.
+struct node* newNode(int data)
+{
+	node* newnode = new node();
+	newnode->data = data;
+	newnode->left = NULL;
+	newnode->right = NULL;
+
+	return (newnode);
+}
+
+// Driver code
+int main()
+{
+	struct node* root = newNode(1);
+	root->left = newNode(2);
+	root->right = newNode(3);
+	root->left->left = newNode(7);
+	root->left->right = newNode(6);
+	root->right->left = newNode(5);
+	root->right->right = newNode(4);
+	printf("Spiral Order traversal of "
+		"binary tree is \n");
+
+	printSpiral(root);
+
+	return 0;
+}
+
+// This code is contributed by samrat2825