298. Binary Tree Longest Consecutive Sequence
Explanation:
- We need to find the length of the longest consecutive sequence path in a binary tree.
- A consecutive sequence is a sequence of nodes from parent to child where the values of the nodes are consecutive integers.
- We can perform a depth-first search (DFS) traversal of the tree to track the consecutive sequence length.
- We pass the current node, the expected value of the next node in the sequence, and the current length of the consecutive sequence.
- If the current node's value is equal to the expected value, we increase the current length by 1.
- We recursively check the left and right children with the updated expected value and length, and return the maximum length from both branches.
- At each node, we compare the current length with the global maximum length. :
class Solution {
int maxLen = 0;
public int longestConsecutive(TreeNode root) {
if (root == null) return 0;
dfs(root, root.val, 0);
return maxLen;
}
private void dfs(TreeNode node, int expected, int length) {
if (node == null) return;
if (node.val == expected) {
length++;
} else {
length = 1;
}
maxLen = Math.max(maxLen, length);
dfs(node.left, node.val + 1, length);
dfs(node.right, node.val + 1, length);
}
}Code Editor (Testing phase)
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