first trial of obilandmark

Former-commit-id: 00a50bdbf407b03dfdc385a848a536559f5966a5

pkg/obistats/random.go

@@ -0,0 +1,25 @@
+package obistats
+
+import "math/rand"
+
+func SampleIntWithoutReplacemant(n, max int) []int {
+
+	draw := make(map[int]int, n)
+
+	for i := 0; i < n; i++ {
+		y := rand.Intn(max)
+		x, ok := draw[y]
+		if ok {
+			y = x
+		}
+		draw[y] = max - 1
+		max--
+	}
+
+	res := make([]int, 0, n)
+	for i := range draw {
+		res = append(res, i)
+	}
+
+	return res
+}