cs: add «875. Koko Eating Bananas»

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

cs/koko-eating-bananas.cs

@@ -0,0 +1,22 @@
+public class Solution {
+    public int MinEatingSpeed(int[] piles, int h) {
+        double getTotal(int hourly) => piles.Sum(p => double.Ceiling(p / (double)hourly));
+
+        int answer = -1;
+
+        int low = 1, high = piles.Max();
+        while (low <= high) {
+            var mid = (low + high) / 2;
+            var total = getTotal(mid);
+
+            if (total <= h) {
+                answer = mid;
+                high = mid - 1;
+            } else {
+                low = mid + 1;
+            }
+        }
+
+        return answer;
+    }
+}