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#ifdef LOCAL
#include <bits/stdc++.h>
using namespace std;
// tree node stuff here...
struct TreeNode {
int val;
TreeNode *left;
TreeNode *right;
TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};
#endif
static int __initialSetup = []()
{
std::ios::sync_with_stdio(false);
cin.tie(NULL);
return 0;
}
();
// handle special cases first
// [], "", ...
// range of input?
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution
{
private:
int dfs(TreeNode *root, int &ans)
{
if (root == NULL)
return 0;
int ret = 0;
int l = dfs(root->left, ans);
int r = dfs(root->right, ans);
if (root->left && root->left->val == root->val)
ret = max(ret, l + 1);
if (root->right && root->right->val == root->val)
ret = max(ret, r + 1);
if (root->left && root->right && root->right->val == root->val &&
root->val == root->left->val)
ans = max(ans, l + 1 + r + 1); // KEY!!
ans = max(ans, ret);
return ret;
}
public:
int longestUnivaluePath(TreeNode *root)
{
int ans = 0;
dfs(root, ans);
return ans;
}
};
#ifdef LOCAL
int main()
{
return 0;
}
#endif
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