llipio#18 solutions and test

test/yourTest.js

@@ -0,0 +1,21 @@
+const expect = require('chai').expect;
+let solution = require('../yourSolution').solution;
+//solution = require('./yourSolution').solution;
+
+describe('missing number', () => {
+  it('the missing number is 7', () => {
+    expect(solution([5,6,8,9])).eql(7);
+  });
+  it('there is no missing number', () => {
+    expect(solution([7,8,9])).eql(null);
+  });
+  it('the missing number is 100', () => {
+    expect(solution([99,101,102,103])).eql(100);
+  });
+  it('the missing number is 1023', () => {
+    expect(solution([1020,1021,1022,1024])).eql(1023);
+  });
+  it('the missing number is -21', () => {
+    expect(solution([-24,-23,-22,-20,-19])).eql(-21)
+  });
+});

yourSolution.js

@@ -1,7 +1,21 @@
-// Name
-// Problem Description
+// Takes in an array and finds the missing consecutive number
 
-const solution = () => {
+// input: [5,6,8,9]
+// output: 7
+
+/**
+ * @param {number[]} arr - an array of consecutive numbers inputted
+ * @return {number} missingNum - the missing number or null if the array has no missing number
+*/
+
+const solution = (arr) => {
+  let missingNum = null;
+  for(let i = 0; i < arr.length - 1; i++){
+    if(arr[i] + 1 !== arr[i + 1]){
+      missingNum = arr[i] + 1;
+    }
+  }
+  return missingNum;
 };
 
 module.exports = {