diff --git a/Problem45.java b/Problem45.java
new file mode 100644
index 00000000..2bf4c838
--- /dev/null
+++ b/Problem45.java
@@ -0,0 +1,36 @@
+// Time Complexity : O(N)
+// Space Complexity : O(N)
+// Did this code successfully run on Leetcode : yes
+// Any problem you faced while coding this : No
+
+class Solution {
+    private Map<Integer, Integer> map;
+    private int postOrderIdx;
+    public TreeNode buildTree(int[] inorder, int[] postorder) {
+        this.map = new HashMap<>();
+        this.postOrderIdx = postorder.length-1;
+        
+        for (int i = 0; i < inorder.length; i++) {
+            map.put(inorder[i],i);
+        }
+
+        return helper(postorder, 0, inorder.length-1);
+    }
+
+    private TreeNode helper(int[] postorder, int start, int end) {
+        //base
+        if (start > end) return null;
+
+        //logic
+        int rootVal = postorder[this.postOrderIdx];
+        int rootIdx = map.get(rootVal);
+        this.postOrderIdx--;
+
+        TreeNode root = new TreeNode(rootVal);
+
+        root.right = helper(postorder, rootIdx + 1, end);
+        root.left = helper(postorder, start, rootIdx - 1);
+
+        return root;
+    }
+}
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diff --git a/Problem46.java b/Problem46.java
new file mode 100644
index 00000000..8913b17e
--- /dev/null
+++ b/Problem46.java
@@ -0,0 +1,25 @@
+// Time Complexity : O(N)
+// Space Complexity : O(h)
+
+class Solution {
+    private int result;
+    public int sumNumbers(TreeNode root) {
+        this.result = 0;
+        helper(root, 0);
+        return result;
+    }
+
+    private void helper(TreeNode root, int currSum) {
+        //base
+        if (root == null) return;
+
+        //logic
+        currSum = currSum * 10 + root.val;
+
+        helper(root.left, currSum);
+                if (root.left == null && root.right == null) {
+            result += currSum;
+        }
+        helper(root.right, currSum);
+    }
+}
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diff --git a/Sample.java b/Sample.java
deleted file mode 100644
index f5c45b5f..00000000
--- a/Sample.java
+++ /dev/null
@@ -1,7 +0,0 @@
-// Time Complexity :
-// Space Complexity :
-// Did this code successfully run on Leetcode :
-// Any problem you faced while coding this :
-
-
-// Your code here along with comments explaining your approach
\ No newline at end of file