# 298. (Locked)Binary Tree Longest Consecutive Sequence

Difficulty: Medium

Frequency: N/A

Given a binary tree, find the length of the longest consecutive sequence path.

The path refers to any sequence of nodes from some starting node to any node in the tree along the parent-child connections. The longest consecutive path need to be from parent to child (cannot be the reverse).

For example,

```   1
\
3
/ \
2   4
\
5
```

Longest consecutive sequence path is `3-4-5`, so return `3`.

```   2
\
3
/
2
/
1
```

Longest consecutive sequence path is `2-3`,not `3-2-1`, so return `2`.

My solution:
Data structure:
Steps:
Complexity:
Runtime:
Space:
Test cases:
Corner cases:
Code:
```class Solution {
public:
int longestConsecutive(TreeNode* root) {
return search(root, NULL, 0);
}
int search(TreeNode* node, TreeNode* parent, int len) {
if (!node) return len;
len = (parent && node->val == parent->val + 1) ? len + 1 : 1;
return max(len, max(search(node->left, node, len), search(node->right, node, len)));
}
};
```

Another solution:
Data structure:
steps:
Complexity:
Runtime:
Space:
Code:

Things to learn: