cs: add «539. Minimum Time Difference»

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

cs/minimum-time-difference.cs

@@ -0,0 +1,42 @@
+using System.Collections.Immutable;
+
+public class Solution {
+    private record Time(int hours, int minutes) {
+        public int Normalized { get => hours * 60 + minutes; }
+
+        public static int Distance(Time a, Time b) =>
+            Math.Abs(b.Normalized - a.Normalized);
+
+        public static bool TryParse(string? s, out Time time) {
+            if (s == null) {
+                goto TimeFailedTryParse;
+            }
+
+            var parts = s.Split(":");
+            if (parts.Length != 2) {
+                goto TimeFailedTryParse;
+            }
+
+            if (int.TryParse(parts[0], out var hours) && int.TryParse(parts[1], out var minutes)) {
+                time = new Time(hours, minutes);
+                return true;
+            }
+
+TimeFailedTryParse:
+            time = new Time(0, 0);
+            return false;
+        }
+    }
+
+    public int FindMinDifference(IList<string> timePoints) {
+        var times = timePoints.Select(t => {
+            Time.TryParse(t, out var time);
+            return time;
+        }).OrderBy(time => time.Normalized).ToImmutableList();
+
+        return Math.Min(
+            24 * 60 - Time.Distance(times.Last(), times.First()),
+            times.Zip(times.Skip(1)).Select(pair => Time.Distance(pair.First, pair.Second)).Min()
+        );
+    }
+}