Added Tree Questions

Trees/Diameter_of_tree.cpp

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+#include <bits/stdc++.h>
+using namespace std;
+
+/* Tree node structure used in the program */
+struct Node
+{
+    int data;
+    Node *left, *right;
+};
+
+/* Function to find height of a tree */
+int height(Node *root, int &ans)
+{
+    if (root == NULL)
+        return 0;
+
+    int left_height = height(root->left, ans);
+
+    int right_height = height(root->right, ans);
+
+    // update the answer, because diameter of a
+    // tree is nothing but maximum value of
+    // (left_height + right_height + 1) for each node
+    ans = max(ans, 1 + left_height + right_height);
+
+    return 1 + max(left_height, right_height);
+}
+
+/* Computes the diameter of binary tree with given root. */
+int diameter(Node *root)
+{
+    if (root == NULL)
+        return 0;
+    int ans = INT_MIN; // This will store the final answer
+    height(root, ans);
+    return ans;
+}
+
+struct Node *newNode(int data)
+{
+    struct Node *node = new Node;
+    node->data = data;
+    node->left = node->right = NULL;
+
+    return (node);
+}
+
+// Driver code
+int main()
+{
+    struct Node *root = newNode(1);
+    root->left = newNode(2);
+    root->right = newNode(3);
+    root->left->left = newNode(4);
+    root->left->right = newNode(5);
+
+    printf("Diameter is %d\n", diameter(root));
+
+    return 0;
+}

Trees/TopView_of_tree.cpp

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+// C++ program to print top
+// view of binary tree
+
+#include <bits/stdc++.h>
+using namespace std;
+
+// Structure of binary tree
+struct Node
+{
+    Node *left;
+    Node *right;
+    int hd;
+    int data;
+};
+
+// function to create a new node
+Node *newNode(int key)
+{
+    Node *node = new Node();
+    node->left = node->right = NULL;
+    node->data = key;
+    return node;
+}
+
+// function should print the topView of
+// the binary tree
+void topview(Node *root)
+{
+    if (root == NULL)
+        return;
+    queue<Node *> q;
+    map<int, int> m;
+    int hd = 0;
+    root->hd = hd;
+
+    // push node and horizontal distance to queue
+    q.push(root);
+
+    cout << "The top view of the tree is : \n";
+
+    while (q.size())
+    {
+        hd = root->hd;
+
+        // count function returns 1 if the container
+        // contains an element whose key is equivalent
+        // to hd, or returns zero otherwise.
+        if (m.count(hd) == 0)
+            m[hd] = root->data;
+        if (root->left)
+        {
+            root->left->hd = hd - 1;
+            q.push(root->left);
+        }
+        if (root->right)
+        {
+            root->right->hd = hd + 1;
+            q.push(root->right);
+        }
+        q.pop();
+        root = q.front();
+    }
+
+    for (auto i = m.begin(); i != m.end(); i++)
+    {
+        cout << i->second << " ";
+    }
+}
+
+
+int main()
+{
+
+    Node *root = newNode(1);
+    root->left = newNode(2);
+    root->right = newNode(3);
+    root->left->right = newNode(4);
+    root->left->right->right = newNode(5);
+    root->left->right->right->right = newNode(6);
+    cout << "Following are nodes in top view of Binary "
+            "Tree\n";
+    topview(root);
+    return 0;
+}