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

Author: everthis

2121-intervals-between-identical-elements.js

@@ -0,0 +1,31 @@
+/**
+ * @param {number[]} arr
+ * @return {number[]}
+ */
+const getDistances = function(arr) {
+  let n = arr.length
+  const pre = Array(n).fill(0), suf = Array(n).fill(0), res = Array(n).fill(0), mp = {}
+  
+  for(let i = 0; i < n; i++) {
+    if(mp[arr[i]] == null) mp[arr[i]] = []
+    mp[arr[i]].push(i)
+  }
+
+  Object.keys(mp).forEach(k => {
+    const idxArr = mp[k]
+    for(let i = 1; i < idxArr.length; i++) {
+      pre[idxArr[i]] = pre[idxArr[i - 1]] + i * (idxArr[i] - idxArr[i - 1])
+    }
+  })
+
+  Object.keys(mp).forEach(k => {
+    const idxArr = mp[k]
+    for(let i = idxArr.length - 2; i >= 0; i--) {
+      suf[idxArr[i]] = suf[idxArr[i + 1]] + (idxArr.length - 1 - i) * (idxArr[i + 1] - idxArr[i])
+    }
+  })
+
+  for(let i = 0; i < n; i++) res[i] = pre[i] + suf[i]
+
+  return res
+};