Support edge case scenerio when numbers are repeated

PermCheck/index.js

@@ -3,9 +3,13 @@ function solution (A) {
  let isPermutation = 1;
  let counters = [1];
 
- A.forEach ((elem) => {
- counters[elem] = (counters[elem] || 0) + 1;
- })
+ for (let i = 0; i < A.length; ++i) {
+ counters[A[i]] = (counters[A[i]] || 0) + 1;
+ if (counters[A[i]] > 1) {
+ isPermutation = 0
+ return isPermutation;
+ }
+ }
 
  for (let i = 0; i < counters.length; ++i) {
  if (!counters[i]) {

PermCheck/test.spec.js

@@ -12,4 +12,9 @@ describe('perm check', () => {
  it ('returns 0 if A contains a single element', () => {
  expect(permCheck([2])).toBe(0);
  })
+
+ it ('returns 0 if A contains a repeated elements', () => {
+ expect(permCheck([2, 2])).toBe(0);
+ expect(permCheck([1, 1])).toBe(0);
+ })
 })