3: top k frequent elements

Author: whewchews

top-k-frequent-elements/whewchews.ts

@@ -0,0 +1,28 @@
+function topKFrequent(nums: number[], k: number): number[] {
+  const dict: Map<number, number> = new Map();
+
+  // TC: O(N)
+  // SC: O(N)
+  nums.forEach((n) => {
+    if (!dict.has(n)) dict.set(n, 1);
+    else {
+      dict.set(n, dict.get(n) + 1);
+    }
+  });
+
+  // TC: O(N)
+  // SC: O(N)
+  const buckets: number[][] = Array(nums.length + 1)
+    .fill(0)
+    .map((_) => []);
+  Array.from(dict.entries()).forEach(([num, cnt]) => {
+    buckets[cnt].push(num);
+  });
+
+  // TC: O(N) + O(k) = O(N)
+  // SC: O(N)
+  return buckets.flat().slice(-k);
+}
+
+// TC: O(N)
+// SC: O(N)