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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?
class Solution
{
private:
// bottom up
int ans = 0;
int dfs(TreeNode *root)
{
if (root == NULL)
return 0;
int l = dfs(root->left);
int r = dfs(root->right);
int mx = 1;
if (root->left && root->left->val == root->val + 1)
mx = max(mx, l + 1);
if (root->right && root->right->val == root->val + 1)
mx = max(mx, r + 1);
ans = max(mx, ans);
return mx;
}
// top down
int dfs(TreeNode *root, TreeNode *parent, int mx)
{
if (root == NULL)
return mx;
if (parent != nullptr && root->val == parent->val + 1)
mx++; // extent the value from parent
else
mx = 1; // reset mx value to self only
return max(mx, max(dfs(root->left, root, mx), dfs(root->right, root, mx)));
}
public:
int longestConsecutive(TreeNode *root)
{
// bottom up
// ans = 0;
// dfs(root);
// return ans;
// top down
return dfs(root, nullptr, 0);
// WA:
// You can't do it directly!
// the case below, node 4 will ret 4 to 3, and then GG
/*
1
\
3
\
4
/ \
9 5
(ret = 4)
*/
// if (root == NULL)
// return 0;
// int mx = 1;
// if (root->left) {
// int ret = longestConsecutive(root->left);
// mx = max(mx, ret + (root->left->val == root->val + 1 ? 1 : 0));
// }
// if (root->right) {
// int ret = longestConsecutive(root->right);
// mx = max(mx, ret + (root->right->val == root->val + 1 ? 1 : 0));
// }
// return mx;
}
};
#ifdef LOCAL
int main()
{
return 0;
}
#endif
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