1. Number of nodes #

Created Monday 27 January 2020

• Tree problems are very easy just **imagine **them like.

Right side is the correct visualization. Left side is the wrong one.

Very easy, plain recursion: template int countNodes(TreeNode *root) { // prank check if (root == NULL) return 0;

// base case if (root->children.size() == 0) return 1; // leaf node

// recursion, return nodes for all children + the root int sum = 0; int children_num = root->children.size(); for (int i = 0; i < children_num; i++) sum += (countNodes(root->children.at(i)));

return sum + 1; // 1 is for the root }

• Recursion is a great tool, use it.