solve: top k frequent elements

Author: tolluset

top-k-frequent-elements/tolluset.ts

@@ -0,0 +1,27 @@
+type Nums = [number, number][];
+
+/*
+ * TC: O(nlogn)
+ * SC: O(n)
+ * */
+function topKFrequent(nums: number[], k: number): number[] {
+  const counting = (arr: number[]) =>
+    arr.reduce((acc, n) => {
+      const val = acc.get(n) ?? 0;
+      acc.set(n, val + 1);
+      return acc;
+    }, new Map<number, number>());
+
+  const toValues = (map: Map<number, number>) => Array.from(map.entries());
+
+  const sorting = (arr: Nums) => arr.sort((a, b) => b[1] - a[1]);
+
+  const getK = (arr: Nums, k: number) => arr.slice(0, k).map((v) => v[0]);
+
+  return pipe(counting, toValues, sorting, (arr: Nums) => getK(arr, k))(nums);
+}
+
+const pipe =
+  (...fns: Function[]) =>
+  (x: any) =>
+    fns.reduce((v, f) => f(v), x);