Add solution to problem sum root to leaf

Author: pulkitent

SumRootToLeaf.java

@@ -0,0 +1,75 @@
+package com.mckinsey.engage.risk.services;
+
+import java.util.LinkedList;
+import java.util.List;
+
+public class SumRootToLeaf {
+    public void main(String[] args) {
+        TreeNode tree = new TreeNode();
+        List<String> allNumbersInString = convertRootToLeadDigitsIntoNumber(tree);
+        int sum = 0;
+        for (String number : allNumbersInString) {
+            sum = sum + Integer.parseInt(number);
+        }
+    }
+
+    public int sumNumbers(TreeNode root) {
+        List<String> allNumbersInString = convertRootToLeadDigitsIntoNumber(root);
+        int sum = 0;
+        for (String number : allNumbersInString) {
+            sum = sum + Integer.parseInt(number);
+        }
+
+        return sum;
+    }
+
+    List<String> convertRootToLeadDigitsIntoNumber(TreeNode root) {
+        if (root == null)
+            return new LinkedList<>();
+
+        if (root.left == null && root.right == null) {
+            LinkedList<String> list = new LinkedList<>();
+            list.add(root.val + "");
+            return list;
+        }
+
+        List<String> rightSubtreeIntegers = convertRootToLeadDigitsIntoNumber(root.left);
+        List<String> leftSubtreeIntegers = convertRootToLeadDigitsIntoNumber(root.right);
+
+        List<String> rootList = new LinkedList<>();
+
+        for (String number : rightSubtreeIntegers) {
+            rootList.add(root.val + number);
+        }
+
+        for (String number : leftSubtreeIntegers) {
+            rootList.add(root.val + number);
+        }
+
+        return rootList;
+    }
+
+    Integer convertRootToLeadDigitsIntoNumber2nd(int sum, TreeNode root, int level) {
+        if (root == null)
+            return 0;
+
+        if (root.left == null && root.right == null) {
+            sum = root.val;
+            return sum;
+        }
+
+        int sumTillNow = (int) ((sum * Math.pow(10, level)) + root.val);
+
+        Integer rightSubtreeSum = convertRootToLeadDigitsIntoNumber2nd(sumTillNow, root.left, level + 1);
+        Integer leftSubtreeSum = convertRootToLeadDigitsIntoNumber2nd(sumTillNow, root.right, level + 1);
+
+        return rightSubtreeSum + leftSubtreeSum;
+    }
+
+
+    class TreeNode {
+        int val;
+        TreeNode left;
+        TreeNode right;
+    }
+}