Create intervals-between-identical-elements.cpp

Author: kamyu104

C++/intervals-between-identical-elements.cpp

@@ -0,0 +1,23 @@
+// Time:  O(n)
+// Space: O(n)
+
+class Solution {
+public:
+    vector<long long> getDistances(vector<int>& arr) {
+        unordered_map<int, vector<long long>> lookup;
+        for (int i = 0; i < size(arr); ++i) {
+            lookup[arr[i]].emplace_back(i);
+        }
+        vector<long long> result(size(arr));
+        for (const auto& [_, idxs] : lookup) {
+            vector<long long> prefix(1);
+            for (const auto& i : idxs) {
+                prefix.emplace_back(prefix.back() + i);
+            }
+            for (int i = 0; i < size(idxs); ++i) {
+                result[idxs[i]] = (idxs[i] * (i + 1) - prefix[i + 1]) + ((prefix[size(idxs)] - prefix[i]) - idxs[i] * (size(idxs) - i));
+            }
+        }
+        return result;
+    }
+};