Add Codility missing element (Go/Java)

Go/jobspls/algorithms/perm_missing_element.go

@@ -0,0 +1,20 @@
+package algorithms
+
+func PermMissingElement(haystack []int) uint {
+	hayset := make(map[int]struct{}, len(haystack))
+
+	for _, v := range haystack {
+		hayset[v] = struct{}{}
+	}
+
+	// Will always return at least element because the loop goes to 
+	// one past haystack's length 
+	for i := 1; i < len(haystack) + 2; i++ {
+		if _, found := hayset[i]; !found {
+			return uint(i)
+		}
+	}
+
+	panic("Unreachable")
+}
+

Java/jobspls/algorithms/PermMissingElement.java

@@ -0,0 +1,21 @@
+package jobspls.algorithms;
+
+import java.util.Arrays;
+import java.util.TreeSet;
+
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+
+public class PermMissingElement {
+    public static int missing_element(int[] haystack) {
+        var hayset = new TreeSet<Integer>(Arrays.stream(haystack)
+                                                .boxed()
+                                                .collect(Collectors.toList()));
+
+        // Should always find a value.
+        return IntStream.range(1, haystack.length + 2)
+                        .filter(n -> { return !hayset.contains(n); })
+                        .findFirst()
+                        .getAsInt();
+    }
+}