Add C++ solution of problem #2579

Author: Cuda-Chen

2579/solution.cpp

@@ -0,0 +1,9 @@
+class Solution {
+public:
+    long long coloredCells(int n) {
+        long long ans = 1;
+        for(int i = 2; i <= n; i++)
+            ans += (i * 4) - 4;
+        return ans;
+    }
+};