cs: add «1792. Maximum Average Pass Ratio»

URL:	https://leetcode.com/problems/maximum-average-pass-ratio/
Signed-off-by: Matej Focko <me@mfocko.xyz>

cs/maximum-average-pass-ratio.cs

@@ -0,0 +1,31 @@
+public class Solution {
+    private record struct ClassRecord(int Passes, int Students) {
+        public double PassRatio => (double)Passes / Students;
+        public double Gain => (double)(Passes + 1) / (Students + 1) - PassRatio;
+    }
+
+    public double MaxAverageRatio(int[][] classes, int extraStudents) {
+        // Construct the max heap based on the effect of adding student
+        var q = new PriorityQueue<ClassRecord, double>();
+        foreach (var classRecord in classes) {
+            var c = new ClassRecord(classRecord[0], classRecord[1]);
+            q.Enqueue(c, -c.Gain);
+        }
+
+        // Add the students based on priority
+        while (extraStudents-- > 0) {
+            var c = q.Dequeue();
+
+            var cWithNewStudent = new ClassRecord(c.Passes + 1, c.Students + 1);
+            q.Enqueue(cWithNewStudent, -cWithNewStudent.Gain);
+        }
+
+        // Calculate final pass ratio
+        double ratio = 0;
+        while (q.TryDequeue(out var c, out var gain)) {
+            ratio += c.PassRatio;
+        }
+
+        return ratio / classes.Length;
+    }
+}