Create 1123. Lowest Common Ancestor of Deepest Leaves

1123. Lowest Common Ancestor of Deepest Leaves

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+/**
+ * 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 {
+public:
+    TreeNode* helper(unordered_set<TreeNode*>&s, TreeNode *root){
+        if(!root) return NULL;
+        if(s.count(root))return root;
+        TreeNode* l = helper(s, root->left);
+        TreeNode* r = helper(s, root->right);
+        if(l && r)return root;
+        return l ? l : r;
+    }
+    TreeNode* lcaDeepestLeaves(TreeNode* root) { 
+        unordered_set<TreeNode*>s;
+        queue<TreeNode*>q;
+        q.push(root);
+        while(q.size()){
+            int n = q.size();
+            s.clear();
+            while(n--){
+                TreeNode* temp = q.front();
+                q.pop();
+                s.insert(temp);
+                if(temp->left) q.push(temp->left);
+                if(temp->right) q.push(temp->right);
+            }
+        }
+        return helper(s, root);
+    }
+};