Create sort-array-by-increasing-frequency.cpp

Author: kamyu104

C++/sort-array-by-increasing-frequency.cpp

@@ -0,0 +1,17 @@
+// Time:  O(nlogn)
+// Space: O(n)
+
+class Solution {
+public:
+    vector<int> frequencySort(vector<int>& nums) {
+        unordered_map<int, int> count;
+        for (const auto& x : nums) {
+            ++count[x];
+        }
+        sort(begin(nums), end(nums),
+             [&count](const auto& a, const auto& b) {
+                 return count[a] == count[b] ? a > b : count[a] < count[b];
+             });
+        return nums;
+    }
+};