Add get first recurring array element func

Signed-off-by: Darko Draskovic <[email protected]>

src/index.js

@@ -2,6 +2,8 @@
 import { doTwoMemSumTo } from './utils.js'
 import { reverseStringLambda } from './utils.js'
 import { mergeSorted } from './utils.js'
+import { getFirstRecurring } from './utils.js'
+import { getFirstRecurringSlow } from './utils.js'
 import { HashTable } from './hash-table.js'
 
 // const arr1 = ['a', 'b', 'c', 'd', 'e'];
@@ -32,4 +34,20 @@ console.log(myHashTable.get('pears'));
 console.log(myHashTable.keys());
 console.log(myHashTable);
 
+console.log("\ngetFirstRecurringSlow");
+console.log((getFirstRecurringSlow([2, 5, 1, 2, 3, 5, 1, 2, 4])));
+console.log((getFirstRecurringSlow([2, 5, 5, 2, 3, 5, 1, 2, 4])));
+console.log((getFirstRecurringSlow([2, 3, 4, 5])));
+console.log((getFirstRecurringSlow([1])));
+console.log((getFirstRecurringSlow([])));
+console.log((getFirstRecurringSlow([1,1])));
+console.log((getFirstRecurringSlow([2,5,4,3,4,5,2,1])));
 
+console.log("\ngetFirstRecurring");
+console.log((getFirstRecurring([2, 5, 1, 2, 3, 5, 1, 2, 4])));
+console.log((getFirstRecurring([2, 5, 5, 2, 3, 5, 1, 2, 4])));
+console.log((getFirstRecurring([2, 3, 4, 5])));
+console.log((getFirstRecurring([1])));
+console.log((getFirstRecurring([])));
+console.log((getFirstRecurring([1,1])));
+console.log((getFirstRecurring([2,5,4,3,4,5,2,1])));

src/utils.js

@@ -56,3 +56,25 @@ export function mergeSorted(a, b) {
  }
  return c.concat(ai < a.length ? b.slice(bi) : a.slice(ai));
 }
+
+export function getFirstRecurringSlow(arr) {
+ let leastIdx = Infinity;
+ for (let i = 0; i < arr.length; i++) {
+ if (i + 1 > leastIdx) break;
+ for (let j = i+1; j < arr.length; j++) {
+ if (arr[i] === arr[j]) {
+ if (j < leastIdx) leastIdx = j;
+ break;
+ }
+ }
+ }
+ return arr[leastIdx];
+}
+
+export function getFirstRecurring(arr) {
+ const occuring = {};
+ for (let i = 0; i < arr.length; i++) {
+ if (occuring[arr[i]]) return arr[i];
+ else occuring[arr[i]] = true;
+ }
+}