Find the distance between two nodes in a binary tree?

Short answer: TreeNode LCA(TreeNode root, int n1, int n2) { if (root == null) return null; if (root.val == n1 || root.val == n2) return root; TreeNode left = LCA(root.left, n1, n2); Follow on: TreeNode right = LCA(root.right, n1, n2); if (left != null && right != null) return root; return left ??

Explain a bit more

right; } int FindLevel(TreeNode root, int val, int level) { if (root == null) return -1; if (root.val == val) return level; int left = FindLevel(root.left, val, level + 1); if (left != -1) return left; return FindLevel(root.right, val, level + 1); } int DistanceBetweenNodes(TreeNode root, int n1, int n2) { TreeNode lca = LCA(root, n1, n2); int d1 = FindLevel(lca, n1, 0); int d2 = FindLevel(lca, n2, 0); return d1 + d2; } Explanation: Find Lowest Common Ancestor (LCA) then sum distances from LCA to each node.

Example code

TreeNode LCA(TreeNode root, int n1, int n2) { if (root == null) return null;
if (root.val == n1 || root.val == n2) return root;
TreeNode left = LCA(root.left, n1, n2); Follow on: TreeNode right = LCA(root.right, n1, n2);
if (left != null && right != null) return root;
return left ?? right;
}
int FindLevel(TreeNode root, int val, int level) {
if (root == null) return -1;
if (root.val == val) return level;
int left = FindLevel(root.left, val, level + 1);
if (left != -1) return left;
return FindLevel(root.right, val, level + 1);
}
int DistanceBetweenNodes(TreeNode root, int n1, int n2) {
TreeNode lca = LCA(root, n1, n2);
int d1 = FindLevel(lca, n1, 0);
int d2 = FindLevel(lca, n2, 0);
return d1 + d2;
} Explanation: Find Lowest Common Ancestor (LCA) then sum distances from LCA to each node.

Real-world example (ShopNest)

In coding rounds, state complexity aloud, write a clear ShopNest-flavored example (orders, carts), then handle edge cases (empty list, null, overflow).

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.