New Problem Solution "Cousins in Binary Tree"

Author: haoel

README.md

@@ -10,6 +10,7 @@ LeetCode
 |---| ----- | -------- | ---------- |
 |1030|[Matrix Cells in Distance Order](https://leetcode.com/problems/matrix-cells-in-distance-order/) | [C++](./algorithms/cpp/matrixCellsInDistanceOrder/MatrixCellsInDistanceOrder.cpp)|Easy|
 |1029|[Two City Scheduling](https://leetcode.com/problems/two-city-scheduling/) | [C++](./algorithms/cpp/twoCityScheduling/TwoCityScheduling.cpp)|Easy|
+|993|[Cousins in Binary Tree](https://leetcode.com/problems/cousins-in-binary-tree/) | [C++](./algorithms/cpp/cousinsInBinaryTree/CousinsInBinaryTree.cpp)|Easy|
 |990|[Satisfiability of Equality Equations](https://leetcode.com/problems/satisfiability-of-equality-equations/) | [C++](./algorithms/cpp/satisfiabilityOfEqualityEquations/SatisfiabilityOfEqualityEquations.cpp)|Medium|
 |989|[Add to Array-Form of Integer](https://leetcode.com/problems/add-to-array-form-of-integer/) | [C++](./algorithms/cpp/addToArrayFormOfInteger/AddToArrayFormOfInteger.cpp)|Easy|
 |988|[Smallest String Starting From Leaf](https://leetcode.com/problems/smallest-string-starting-from-leaf/) | [C++](./algorithms/cpp/smallestStringStartingFromLeaf/SmallestStringStartingFromLeaf.cpp)|Medium|

algorithms/cpp/cousinsInBinaryTree/CousinsInBinaryTree.cpp

@@ -0,0 +1,74 @@
+// Source : https://leetcode.com/problems/cousins-in-binary-tree/
+// Author : Hao Chen
+// Date   : 2019-04-30
+
+/***************************************************************************************************** 
+ *
+ * In a binary tree, the root node is at depth 0, and children of each depth k node are at depth k+1.
+ * 
+ * Two nodes of a binary tree are cousins if they have the same depth, but have different parents.
+ * 
+ * We are given the root of a binary tree with unique values, and the values x and y of two different 
+ * nodes in the tree.
+ * 
+ * Return true if and only if the nodes corresponding to the values x and y are cousins.
+ * 
+ * Example 1:
+ * 
+ * Input: root = [1,2,3,4], x = 4, y = 3
+ * Output: false
+ * 
+ * Example 2:
+ * 
+ * Input: root = [1,2,3,null,4,null,5], x = 5, y = 4
+ * Output: true
+ * 
+ * Example 3:
+ * 
+ * Input: root = [1,2,3,null,4], x = 2, y = 3
+ * Output: false
+ * 
+ * Note:
+ * 
+ * 	The number of nodes in the tree will be between 2 and 100.
+ * 	Each node has a unique integer value from 1 to 100.
+ * 
+ ******************************************************************************************************/
+
+/**
+ * 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;
+    }
+};