feat: add cpp solution to lc problem: No.3068 (doocs#2840)

Author: AlleyNawaz

solution/3000-3099/3068.Find the Maximum Sum of Node Values/README_EN.md

@@ -109,7 +109,35 @@ It can be shown that 9 is the maximum achievable sum of values.
 #### C++
 
 ```cpp
-
+class Solution {
+public:
+    long long maximumValueSum(vector<int>& nums, int k,
+                              vector<vector<int>>& edges) {
+        long long totalSum = 0;
+        int count = 0;
+        int positiveMin = INT_MAX;
+        int negativeMax = INT_MIN;
+
+        for (int nodeValue : nums) {
+            int nodeValAfterOperation = nodeValue ^ k;
+            totalSum += nodeValue;
+            int netChange = nodeValAfterOperation - nodeValue;
+
+            if (netChange > 0) {
+                positiveMin = min(positiveMin, netChange);
+                totalSum += netChange;
+                count += 1;
+            } else {
+                negativeMax = max(negativeMax, netChange);
+            }
+        }
+
+        if (count % 2 == 0) {
+            return totalSum;
+        }
+        return max(totalSum - positiveMin, totalSum + negativeMax);
+    }
+};
 ```
 
 #### Go