Time: 17 ms (28.00%), Space: 14.4 MB (35.17%) - LeetHub

0236-lowest-common-ancestor-of-a-binary-tree/0236-lowest-common-ancestor-of-a-binary-tree.cpp

@@ -0,0 +1,66 @@
+/**
+ * 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:
+    TreeNode* ans;
+    bool flag=true;
+    bool chk(TreeNode* root, TreeNode* qu)
+    {
+        if(root==qu)return true;
+        if(root==NULL)return false;
+        bool a=chk(root->left,qu);
+        bool b= chk(root->right, qu);
+        return a || b;
+    }
+
+    bool solve(TreeNode* root, TreeNode* p,TreeNode* q)
+    {
+        if(root==NULL)return false;
+
+        if(root==p)
+        {
+            if(chk(root,q))
+            {
+                ans=root;
+
+                return true;
+            }
+            else
+                return true;
+        }
+        else if(root==q)
+        {
+            if(chk(root,p))
+            {
+                ans=root;
+
+                return true;
+            }
+            else
+                return true;
+        }
+        bool a=solve(root->left,p,q);
+
+        bool b=solve(root->right,p,q);
+        if(a==true && b==true && flag )
+        {
+            ans=root;
+            flag=false;
+        }
+        return a||b;
+    }
+    TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {
+
+        solve(root, p,q);
+
+        return ans;
+
+    }
+};