Add week 1 solutions: top-k-frequent-elements

Author: gitsunmin

top-k-frequent-elements/gitsunmin.ts

@@ -0,0 +1,22 @@
+/**
+ * https://leetcode.com/problems/top-k-frequent-elements/
+ * time complexity : O(n)
+ * space complexity : O(n)
+ */
+function topKFrequent(nums: number[], k: number): number[] {
+    const record = nums.reduce((acc, curr) => {
+        acc[curr] = (acc[curr] ?? 0) + 1;
+        return acc;
+    }, {});
+
+    const array: Array<number[]> = new Array(nums.length);
+    for (const num in record) {
+        const v = record[num];
+        if (!array[v]) {
+            array[v] = [];
+        }
+        array[v].push(Number(num));
+    }
+
+    return array.reduce((acc, curr) => [...curr, ...acc], []).slice(0, k);
+};