Cousins in Binary Tree Solutions in C++

// Source : https://leetcode.com/problems/cousins-in-binary-tree/
// Author : Hao Chen
// Date   : 2019-04-30



/**
 * 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 dx=0, dy=0;
        TreeNode *px=root, *py=root;
        dx = DepthAndParent(root, px, 0, x);
        dy = DepthAndParent(root, py, 0, y);
        if (dx && dy){
            return (dx == dy && px != py);
        }

        return false;

    }

    int DepthAndParent(TreeNode* root, TreeNode*& parent, int depth, int x) {
        if (!root) return 0;
        if ( root->val == x) return depth;

        int d=0;
        parent = root;
        if  ( ( d = DepthAndParent(root->left, parent, depth+1, x)) > 0 ) return d;

        parent = root;
        if ( ( d = DepthAndParent(root->right, parent, depth+1, x)) > 0 ) return d;
        return 0;
    }
};

/// Source : https://leetcode.com/problems/cousins-in-binary-tree/
/// Author : liuyubobobo
/// Time   : 2019-02-16

#include <iostream>
#include <cassert>

using namespace std;


/// Two-Pass DFS
/// Time Complexity: O(n)
/// Space Complexity: 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) {

        if(!root || root->val == x || root->val == y)
            return false;

        pair<int, int> p1; // depth, parent
        if(!dfs(root, x, 0, p1)) return false;

        pair<int, int> p2;
        if(!dfs(root, y, 0, p2)) return false;

        return p1.first == p2.first && p1.second != p2.second;
    }

private:
    bool dfs(TreeNode* node, int x, int d, pair<int, int>& p){

        if(node->left && node->left->val == x){
            p = make_pair(d + 1, node->val);
            return true;
        }

        if(node->right && node->right->val == x){
            p = make_pair(d + 1, node->val);
            return true;
        }

        if(node->left && dfs(node->left, x, d + 1, p))
            return true;

        if(node->right && dfs(node->right, x, d + 1, p))
            return true;

        return false;
    }
};


int main() {

    return 0;
}

/// Source : https://leetcode.com/problems/cousins-in-binary-tree/
/// Author : liuyubobobo
/// Time   : 2019-02-18

#include <iostream>
#include <cassert>
#include <unordered_map>

using namespace std;


/// One-Pass DFS
/// Using HashMap to record the result :-)
///
/// Time Complexity: O(n)
/// Space Complexity: O(n)

/// 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) {

        if(!root || root->val == x || root->val == y)
            return false;

        unordered_map<int, pair<int, int>> record; // depth, parent
        dfs(root, 0, record);

        return record[x].first == record[y].first && record[x].second != record[y].second;
    }

private:
    void dfs(TreeNode* node, int d, unordered_map<int, pair<int, int>>& record){

        if(node->left) {
            record[node->left->val] = make_pair(d + 1, node->val);
            dfs(node->left, d + 1, record);
        }

        if(node->right){
            record[node->right->val] = make_pair(d + 1, node->val);
            dfs(node->right, d + 1, record);
        }
    }
};


int main() {

    return 0;
}