[Leetcode - Easy] Rank Transform of an Array

suhwan2004/Rank Transform of an Array.js

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+/**
+ * @param {number[]} arr
+ * @return {number[]}
+ */
+
+/*
+N === arr.length
+Time : O(NlogN), Space : O(N)
+ALGO : for
+DS : hashMap, Array
+Constraints
+ - 0 <= arr.length <= 10^5
+ - -10^9 <= arr[i] <= 10^9
+Edge Case : arr.length === 0 일시, return arr
+*/
+var arrayRankTransform = function (arr) {
+  if (arr.length === 0) {
+    return arr;
+  }
+  const sortMap = new Map();
+  const sortArr = [...arr].sort((a, b) => a - b);
+
+  let rank = 1;
+  for (let i = 0; i < sortArr.length; i++) {
+    if (i !== 0 && sortArr[i] !== sortArr[i - 1]) {
+      rank++;
+    }
+    sortMap.set(sortArr[i], rank);
+  }
+  return arr.map((cur) => sortMap.get(cur));
+};