Add week 5 soultions : topKFrequentElements

Author: yolophg

top-k-frequent-elements/yolophg.js

@@ -0,0 +1,28 @@
+// Time Complexity: O(n)
+// Space Complexity: O(m)
+
+var topKFrequent = function(nums, k) {
+    const frequencyMap = new Map();
+    // for each number in the array, update frequency.
+    for (const num of nums) {
+        frequencyMap.set(num, (frequencyMap.get(num) || 0));
+    }
+
+    // create buckets where index represents frequency.
+    const buckets = Array(nums.length + 1).fill().map(() => []);
+    // place each number into the bucket corresponding to frequency.
+    for (const [num, frequency] of frequencyMap.entries()) {
+        buckets[frequency].push(num);
+    }
+
+    const result = [];
+    // iterate from the highest possible frequency down to the lowest.
+    for (let i = buckets.length - 1; i >= 0 && result.length < k; i--) {
+        if (buckets[i].length > 0) {
+            result.push(...buckets[i]);
+        }
+    }
+
+    // ensure the result length is k.
+    return result.slice(0, k); 
+};