Thoda bhot hi samajh aya, will revisit it again.

Author: ChSatyaSavith

863. All Nodes Distance K in Binary Tree.cpp

@@ -0,0 +1,59 @@
+class Solution {
+public:
+    vector<int> distanceK(TreeNode* root, TreeNode* target, int k) {
+        vector<int> ans;
+        unordered_map<int, TreeNode*> parent;
+        queue<TreeNode*> q;
+        q.push(root);
+
+        while(!q.empty()){
+            int si = q.size();
+            for(int i = 0; i < si; i++){
+                auto top = q.front();
+                q.pop();
+                
+                if(top -> left){
+                    parent[top->left->val] = top;
+                    q.push(top->left); 
+                }
+
+                if(top -> right){
+                    parent[top->right->val] = top;
+                    q.push(top->right); 
+                }
+            }
+        }
+
+        unordered_map<int, int> visited;
+        q.push(target);
+        while(k-- && !q.empty()){
+            int size = q.size();
+
+            for(int i = 0; i < size; i++){
+                auto top = q.front();
+                q.pop();
+
+                visited[top -> val] = 1;
+
+                if(top -> left && !visited[top->left->val]){
+                    q.push(top -> left);
+                }
+
+                if(top -> right && !visited[top->right->val]){
+                    q.push(top -> right);
+                }
+
+                if(parent[top->val] && !visited[parent[top->val] -> val]){
+                    q.push(parent[top->val]);
+                }
+
+            }
+        }
+
+        while(!q.empty()){
+            ans.push_back(q.front()->val);
+            q.pop();
+        }
+        return ans;
+    }
+};