Finished an array problem

Author: PalmaAnd

Diff for: js/Problems/containsDuplicate.js

@@ -0,0 +1,46 @@
+/**
+ * Runtime efficient version.
+ * I never learned what a set is until now: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set?retiredLocale=de
+ * A set works good in this case, because it can never have an element twice.
+ * 
+ * @param {number[]} nums
+ * @return {boolean}
+ */
+var containsDuplicate = function(nums) {
+    let helperarr = new Set();
+    for (const element of nums){
+        if(helperarr.has(element))
+            return true;
+        else
+            helperarr.add(element);
+    }
+    return false;
+};
+
+/**
+ * A solution that is 50/50 between memory and runtime
+ * 
+ * @param {number[]} nums
+ * @return {boolean}
+ */
+var containsDuplicate3 = function(nums) {
+    let set = new Set(nums);
+    return set.size != nums.length;
+};
+
+/**
+ * Memory efficient version
+ * 
+ * @param {number[]} nums
+ * @return {boolean}
+ */
+var containsDuplicate2 = function(nums) {
+    let helperarr = [];
+    for (let i = 0; i < nums.length; i++){
+        if(helperarr.includes(nums[i]))
+            return true;
+        else
+            helperarr[i] = nums[i];
+    }
+    return false;
+};