Added 2 solutions

Author: varunu28

Easy/Decompress Run-Length Encoded List.java

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+class Solution {
+  public int[] decompressRLElist(int[] nums) {
+    int count = 0;
+    for (int i = 0; i < nums.length; i += 2) {
+      count += nums[i];
+    }
+    int idx = 0;
+    int[] ans = new int[count];
+    for (int i = 1; i < nums.length; i+= 2) {
+      int freq = nums[i - 1];
+      int val = nums[i];
+      while (freq-- > 0) {
+        ans[idx++] = val;
+      }
+    }
+    return ans;
+  }
+}

Medium/Sum of Nodes with Even-Valued Grandparent.java

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+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode(int x) { val = x; }
+ * }
+ */
+class Solution {
+  public int sumEvenGrandparent(TreeNode root) {
+    int[] ans = {0};
+    helper(root, -1, -1, ans);
+    return ans[0];
+  }
+  
+  private void helper(TreeNode root, int parent, int grandparent, int[] ans) {
+    if (root == null) {
+      return;
+    }
+    if (grandparent > 0 && grandparent % 2 == 0) {
+      ans[0] += root.val;
+    }
+    grandparent = parent;
+    parent = root.val;
+    helper(root.left, parent, grandparent, ans);
+    helper(root.right, parent, grandparent, ans);
+  }
+}