Given a binary tree, find the length of the longest path where each node in the path has the same value. This path may or may not pass through the root.
Note: The length of path between two nodes is represented by the number of edges between them.
Example 1:
Input:
5 / 4 5 / \ 1 1 5
Output:
2
Example 2:
Input:
1 / 4 5 / \ 4 4 5
Output:
2
Note: The given binary tree has not more than 10000 nodes. The height of the tree is not more than 1000.
class Solution { public: int longestUnivaluePath(TreeNode* root) { int lup = 0; if (root) dfs(root, lup); return lup; } private: int dfs(TreeNode* node, int& lup) { int l = node->left ? dfs(node->left, lup) : 0; int r = node->right ? dfs(node->right, lup) : 0; int resl = node->left && node->left->val == node->val ? l + 1 : 0; int resr = node->right && node->right->val == node->val ? r + 1 : 0; lup = max(lup, resl + resr); return max(resl, resr); } };