go: add «1608. Special Array With X Elements Greater Than or Equal X»

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

go/special-array-with-x-elements-greater-than-or-equal-x.go

@@ -0,0 +1,37 @@
+package special_array_with_x_elements_greater_than_or_equal_x
+
+import (
+	"slices"
+)
+
+func specialArray(nums []int) int {
+	bsearch := func(key int) int {
+		l := 0
+		r := len(nums) - 1
+
+		idx := len(nums)
+		for l <= r {
+			mid := (l + r) / 2
+
+			if nums[mid] >= key {
+				idx = mid
+				r = mid - 1
+			} else {
+				l = mid + 1
+			}
+		}
+
+		return idx
+	}
+
+	slices.Sort(nums)
+	for i, _ := range nums {
+		k := bsearch(i + 1)
+
+		if len(nums)-k == i+1 {
+			return i + 1
+		}
+	}
+
+	return -1
+}