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cousins-in-binary-tree.cpp
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cousins-in-binary-tree.cpp
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// Time: O(n)
// Space: O(h)
/**
* 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 {
public:
bool isCousins(TreeNode* root, int x, int y) {
int depth_x = 0, depth_y = 0;
TreeNode *parent_x = nullptr, *parent_y = nullptr;
return dfs(root, x, &depth_x, &parent_x) &&
dfs(root, y, &depth_y, &parent_y) &&
depth_x == depth_y &&
parent_x != parent_y;
}
private:
bool dfs(TreeNode *root, int x, int *depth, TreeNode **parent) {
if (!root) {
return false;
}
if (root->val == x) {
return true;
}
++(*depth);
auto prev_parent = (*parent);
(*parent) = root;
if (dfs(root->left, x, depth, parent)) {
return true;
}
(*parent) = root;
if (dfs(root->right, x, depth, parent)) {
return true;
}
(*parent) = prev_parent;
--(*depth);
return false;
}
};