Create 2013-Detect-Squares.cs

csharp/2013-Detect-Squares.cs

@@ -0,0 +1,35 @@
+public class DetectSquares {
+
+  private Dictionary<(int x, int y), int> _pointsCounter = new();
+    private List<(int x, int y)> _points = new();
+
+    public DetectSquares() { }
+
+    public void Add(int[] point) {
+        var p = (point[0], point[1]);
+        _points.Add(p);
+        _pointsCounter[p] = 1 + _pointsCounter.GetValueOrDefault(p, 0);
+    }
+
+    public int Count(int[] point) {
+        int px = point[0], py = point[1];
+        int result = 0;
+
+        foreach (var (x, y) in _points) {
+
+            if (Math.Abs(px - x) != Math.Abs(py - y) 
+                || x == px || y == py) { 
+                continue;
+            }
+            result += _pointsCounter.GetValueOrDefault((px, y), 0) * _pointsCounter.GetValueOrDefault((x, py), 0);
+        }
+        return result;
+    }
+}
+
+/**
+ * Your DetectSquares object will be instantiated and called as such:
+ * DetectSquares obj = new DetectSquares();
+ * obj.Add(point);
+ * int param_2 = obj.Count(point);
+ */