Create Solution.java

Author: Jerring

solution/0652.Find Duplicate Subtrees/Solution.java

@@ -0,0 +1,19 @@
+class Solution {
+    public List<TreeNode> findDuplicateSubtrees(TreeNode root) {
+        List<TreeNode> res = new ArrayList<>();
+        dfs(root, new HashMap<>(), res);
+        return res;
+    }
+
+    private String dfs(TreeNode root, Map<String, Integer> map, List<TreeNode> res) {
+        if (root == null) {
+            return "";
+        }
+        String s = root.val + "_" + dfs(root.left, map, res) + "_" + dfs(root.right, map, res);
+        map.put(s, map.getOrDefault(s, 0) + 1);
+        if (map.get(s) == 2) {
+            res.add(root);
+        }
+        return s;
+    }
+}