cs: add «3016. Minimum Number of Pushes to Type Word II»

Signed-off-by: Matej Focko <me@mfocko.xyz>

cs/minimum-number-of-pushes-to-type-word-ii.cs

@@ -0,0 +1,33 @@
+public class Solution {
+    private int[] GetFreqs(string word) {
+        var freqs = new int[26];
+        foreach (char c in word) {
+            ++freqs[c - 'a'];
+        }
+        return freqs;
+    }
+
+    public int MinimumPushes(string word) {
+        // Count occurences of letters
+        var freqs = GetFreqs(word);
+
+        // Sort them (letters don't matter, only counts)
+        Array.Sort(freqs);
+
+        var pushes = 0;
+
+        var (minPushes, used) = (1, 0);
+        for (var i = freqs.Length - 1; i >= 0 && freqs[i] > 0; --i) {
+            pushes += freqs[i] * minPushes;
+            ++used;
+
+            // used all buttons for the current position
+            if (used >= 8) {
+                ++minPushes;
+                used = 0;
+            }
+        }
+
+        return pushes;
+    }
+}