top-k-frequent-elements solution

Author: togo26

top-k-frequent-elements/togo26.js

@@ -0,0 +1,52 @@
+/**
+ * @param {number[]} nums
+ * @param {number} k
+ * @return {number[]}
+ */
+
+/*
+TC: O(nlogn) -> sort
+SC: O(n) => numsCount 생성
+*/
+var topKFrequent = function (nums, k) {
+  const numsCount = nums.reduce((acc, cur) => {
+    acc[cur] = acc[cur] + 1 || 1;
+    return acc;
+  }, {});
+
+  const frequecyOrder = Object.entries(numsCount)
+    .sort(([, a], [, b]) => b - a)
+    .map(([k, v]) => [Number(k), v]);
+
+  const result = [];
+
+  for (let i = 0; i < k; i++) result.push(frequecyOrder[i][0]);
+
+  return result;
+};
+
+/*
+TC: O(n) -> frequency bucket index로 활용
+SC: O(n)
+*/
+var topKFrequent = function (nums, k) {
+  const numsCount = nums.reduce((acc, cur) => {
+    acc[cur] = acc[cur] + 1 || 1;
+    return acc;
+  }, {});
+
+  const bucket = [];
+  Object.entries(numsCount).forEach(([num, freq]) => {
+    if (!bucket[freq]) bucket[freq] = [];
+    bucket[freq].push(Number(num));
+  });
+
+  const result = [];
+  for (let i = bucket.length - 1; i >= 0 && result.length < k; i--) {
+    if (Array.isArray(bucket[i])) {
+      result.push(...bucket[i]);
+    }
+  }
+
+  return result;
+};