Tree 3

Problem1.java

@@ -0,0 +1,40 @@
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Problem1 {
+    List<List<Integer>> result;
+    List<Integer> localResult;
+    public List<List<Integer>> pathSum(TreeNode root, int targetSum) {
+        result = new ArrayList<>();
+        localResult = new ArrayList<>();
+        helper(root, 0, targetSum, localResult);
+        return result;
+    }
+
+    private void helper(TreeNode root, int sum, int targetSum, List<Integer> localResult ) {
+        // base case
+        if(root == null) return;
+        //logic 
+        localResult.add(root.val);
+        sum += root.val;
+
+        if(root.left == null && root.right == null && sum == targetSum) {
+            result.add(new ArrayList<>(localResult));
+        }
+        helper(root.left, sum, targetSum, new ArrayList<>(localResult));
+        helper(root.right, sum, targetSum, new ArrayList<>(localResult));
+        localResult.remove(localResult.size() -1);
+    }
+}

Problem2.java

@@ -0,0 +1,41 @@
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Problem2 {
+    boolean flag;
+    public boolean isSymmetric(TreeNode root) {
+        if(root == null) return true;
+        this.flag = true;
+        helper(root.left, root.right);
+        return flag;
+    }
+
+    private void helper(TreeNode left, TreeNode right){
+        if(left == null && right == null) return;
+        if(left == null || right == null){
+            flag = false;
+            return;
+        }
+        if(left.val != right.val){
+            flag = false;
+        }
+
+        if(flag)
+            helper(left.left, right.right);
+
+        if(flag)
+            helper(left.right, right.left);
+    }
+}