Update 2121-intervals-between-identical-elements.js

Author: everthis

2121-intervals-between-identical-elements.js

@@ -1,3 +1,41 @@
+/**
+ * @param {number[]} arr
+ * @return {number[]}
+ */
+const getDistances = function(arr) {
+  const hash = {}
+  const n = arr.length
+  for(let i = 0; i < n; i++) {
+    const e = arr[i]
+    if(hash[e] == null) hash[e] = []
+    hash[e].push(i)
+  }
+  const res = []
+  for(const [k, v] of Object.entries(hash)) {
+    helper(v)
+  }
+  return res
+  
+  function helper(idxArr) {
+    let sum = 0
+    const len = idxArr.length
+    for(let i = 1; i < len; i++) {
+      sum += idxArr[i] - idxArr[0]
+    }
+    const first = idxArr[0]
+    res[first] = sum
+    for(let i = 1; i < len; i++) {
+      const pre = res[idxArr[i - 1]]
+      const delta = idxArr[i] - idxArr[i - 1]
+      const tmp = pre + i * delta - (len - i) * delta
+      res[idxArr[i]] = tmp
+    }
+  }
+};
+
+// another
+
+
 /**
  * @param {number[]} arr
  * @return {number[]}