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1372.longest-zig-zag-path-in-a-binary-tree.cpp
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1372.longest-zig-zag-path-in-a-binary-tree.cpp
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/*
* @lc app=leetcode id=1372 lang=cpp
*
* [1372] Longest ZigZag Path in a Binary Tree
*/
// @lc code=start
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode() : val(0), left(nullptr), right(nullptr) {}
* TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
* TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
* };
*/
#define LEFT 1
#define RIGHT 2
class Solution {
public:
int longestZigZag(TreeNode* root, int direction=0) {
if (!root)return -1;
if (direction == 0){
if (root->left)
ans = max(ans, longestZigZag(root->left, LEFT) + 1);
if (root->right)
ans = max(ans, longestZigZag(root->right, RIGHT) + 1);
return ans;
}
else if (direction == LEFT){
if (root->left)
ans = max(ans, longestZigZag(root->left, LEFT) + 1);
if (root->right)
return longestZigZag(root->right, RIGHT) + 1;
else
return 0;
}
else{ // direction == RIGHT
if (root->right)
ans = max(ans, longestZigZag(root->right, RIGHT) + 1);
if (root->left)
return longestZigZag(root->left, LEFT) + 1;
else
return 0;
}
}
private:
int ans = 0;
};
// @lc code=end