cpp: add “2870. Minimum Number of Operations to Make Array Empty”

Signed-off-by: Matej Focko <mfocko@redhat.com>

cpp/minimum-number-of-operations-to-make-array-empty.cpp

@@ -0,0 +1,32 @@
+#include <map>
+#include <vector>
+
+class Solution {
+  public:
+    int minOperations(const std::vector<int> &nums) {
+        std::map<int, int> freqs;
+        for (const auto &x : nums) {
+            ++freqs[x];
+        }
+
+        int operations = 0;
+
+        for (const auto &[_, count] : freqs) {
+            if (count == 1) {
+                return -1;
+            }
+
+            switch (count % 3) {
+            case 0:
+                operations += count / 3;
+                break;
+            case 1:
+            case 2:
+                operations += count / 3 + 1;
+                break;
+            }
+        }
+
+        return operations;
+    }
+};