Find the first non-consecutive number

8_kyu/Find the first non-consecutive number/README.md

@@ -0,0 +1,24 @@
+## Find the first non-consecutive number
+
+https://www.codewars.com/kata/58f8a3a27a5c28d92e000144
+
+Your task is to find the first element of an array that is not consecutive.
+
+By not consecutive we mean not exactly 1 larger than the previous element of the array.
+
+E.g. If we have an array [1,2,3,4,6,7,8] then 1 then 2 then 3 then 4 are all consecutive but 6 is not, so that's the first non-consecutive number.
+
+If the whole array is consecutive then return null2.
+
+The array will always have at least 2 elements1 and all elements will be numbers. The numbers will also all be unique and in ascending order. The numbers could be positive or negative and the first non-consecutive could be either too!
+
+If you like this Kata, maybe try this one next: https://www.codewars.com/kata/represent-array-of-numbers-as-ranges
+
+1 Can you write a solution that will return null2 for both [] and [ x ] though? (This is an empty array and one with a single number and is not tested for, but you can write your own example test. )
+
+2
+Swift, Ruby and Crystal: nil
+Haskell: Nothing
+Python, Rust, Scala: None
+Julia: nothing
+Nim: none(int) (See options)

8_kyu/Find the first non-consecutive number/index.test.ts

@@ -0,0 +1,13 @@
+import { firstNonConsecutive } from "./index";
+
+describe("Tests", () => {
+    it("a simple example", function () {
+        const first = firstNonConsecutive([1, 2, 3, 4, 6, 7, 8]);
+        expect(first).toBe(6);
+    });
+
+    it("all sequential", function () {
+        const first = firstNonConsecutive([1, 2, 3, 4]);
+        expect(first).toBe(null);
+    });
+});

8_kyu/Find the first non-consecutive number/index.ts

@@ -0,0 +1,9 @@
+export function firstNonConsecutive(arr: number[]) {
+    for (let i = 1; i < arr.length; i++) {
+        if (arr[i - 1] + 1 !== arr[i]) {
+            return arr[i];
+        }
+    }
+
+    return null;
+}

README.md

@@ -2,8 +2,8 @@
 
 ### Katas solved
 
-`Total`: 49 \
-`8_kyu`: 47 \
+`Total`: 50 \
+`8_kyu`: 48 \
 `7_kyu`: 0 \
 `6_kyu`: 2 \
 `5_kyu`: 0 \