cpp: add «2948. Make Lexicographically Smallest Array by Swapping Elements»

URL:	https://leetcode.com/problems/make-lexicographically-smallest-array-by-swapping-elements/
Signed-off-by: Matej Focko <me@mfocko.xyz>

cpp/evaluate-reverse-polish-notation.cpp

@@ -4,8 +4,8 @@
 #include <vector>
 
 class Solution {
-    static auto
-    get_function(const std::string &op) -> std::function<int(int, int)> {
+    static auto get_function(const std::string &op)
+        -> std::function<int(int, int)> {
         if (op == "+") {
             return std::plus<int>{};
         } else if (op == "-") {

cpp/make-lexicographically-smallest-array-by-swapping-elements.cpp

@@ -0,0 +1,37 @@
+#include <algorithm>
+#include <list>
+#include <unordered_map>
+#include <vector>
+
+class Solution {
+  public:
+    auto lexicographicallySmallestArray(std::vector<int> nums, int limit)
+        -> std::vector<int> {
+        // sort the numbers
+        auto sorted_nums = nums;
+        std::sort(sorted_nums.begin(), sorted_nums.end());
+
+        // assign groups
+        std::unordered_map<int, int> num_to_group;
+        std::unordered_map<int, std::list<int>> groups;
+
+        auto group = 0;
+        for (auto i = 0u; i < sorted_nums.size(); ++i) {
+            if (i > 0 && sorted_nums[i] - sorted_nums[i - 1] > limit) {
+                ++group;
+            }
+
+            num_to_group[sorted_nums[i]] = group;
+            groups[group].push_back(sorted_nums[i]);
+        }
+
+        // emplace into original ‹nums›
+        for (auto &x : nums) {
+            group = num_to_group[x];
+            x = *groups[group].begin();
+            groups[group].pop_front();
+        }
+
+        return nums;
+    }
+};