Merge pull request #24 from Bill0412/patch-5

Create 1740.Find-Distance-in-a-Binary-Tree_v2.cpp

Author: wisdompeak

Tree/1740.Find-Distance-in-a-Binary-Tree/1740.Find-Distance-in-a-Binary-Tree_v2.cpp

@@ -0,0 +1,34 @@
+/**
+ * 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) {}
+ * };
+ */
+class Solution {
+    int lcaDepth = -1, pDepth, qDepth;
+    TreeNode* lcaNode;
+    int lowestCommonAncestor(TreeNode* root, int p, int q, int depth) {
+        if(!root) return 0;
+
+        int count = lowestCommonAncestor(root->left, p, q, depth + 1) + 
+                    lowestCommonAncestor(root->right, p, q, depth + 1) +
+                    (root->val == p) + (root->val == q);
+
+        if(root->val == p) pDepth = depth; 
+        if(root->val == q) qDepth = depth;
+        if(count == 2 && lcaDepth == -1) lcaDepth = depth;
+        
+        return count;
+    }
+public:
+    int findDistance(TreeNode* root, int p, int q) {
+        lowestCommonAncestor(root, p, q, 0);
+
+        return (pDepth - lcaDepth) + (qDepth - lcaDepth);
+    }
+};