C16 - Afina Walton

lib/exercises.js

@@ -1,19 +1,54 @@
 // This method will return an array of arrays.
 // Each subarray will have strings which are anagrams of each other
-// Time Complexity: ?
-// Space Complexity: ?
+// Time Complexity: O(N^2)
+// Space Complexity: O(N^2)
 function groupedAnagrams(strings) {
-    throw new Error("Method hasn't been implemented yet!");
+    let counter = {};
+    let grouped = []
+    for (let str of strings) {
+        // separates each string into array - O(N^2) operation
+        const sorted = [...str].sort().join('');
+        if (!counter[sorted]) counter[sorted] = [str];
+        else counter[sorted].push(str);
+    }
+
+    for (let value of Object.values(counter)) {
+        grouped.push(value)
+    }
+
+    return grouped
 }
 
 // This method will return the k most common elements
 // in the case of a tie it will select the first occuring element.
-// Time Complexity: ?
-// Space Complexity: ?
-function topKFrequentElements(list, k) {
-    throw new Error("Method hasn't been implemented yet!");
+// Time Complexity: O(N)
+// Space Complexity: O(N)
+function createCounter(arr) {
+    let counter = {};
+
+    for (let num of arr) {
+        if (counter[num]) counter[num]++;
+        else counter[num] = 1;
+    }
+
+    return counter
 }
 
+function sortObject(counter) {
+    let counterArray = Object.entries(counter).map(element => +element[0]);
+
+    counterArray.sort((a, b) => b[1] - a[1]);
+
+    return counterArray
+}
+
+function topKFrequentElements(list, k) {
+    const counter = createCounter(list);
+    const sorted = sortObject(counter);
+
+    return sorted.slice(0, k);
+
+}
 
 // This method will return true if the table is still
 //   a valid sudoku table.