add new solutions

solutions/21/q2154/solution.go

@@ -0,0 +1,16 @@
+package q2154
+
+import "slices"
+
+func findFinalValue(nums []int, original int) int {
+	slices.Sort(nums)
+
+	for i := range nums {
+		if nums[i] == original {
+			original *= 2
+		}
+	}
+	return original
+}
+
+var _ = findFinalValue