cpp: add «49. Group Anagrams»

Signed-off-by: Matej Focko <me@mfocko.xyz>

cpp/group-anagrams.cpp

@@ -0,0 +1,26 @@
+#include <algorithm>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+class Solution {
+    using words_t = std::vector<std::string>;
+
+  public:
+    std::vector<words_t> groupAnagrams(const words_t &strs) {
+        std::unordered_map<std::string, words_t> groups;
+        for (const auto &s : strs) {
+            std::string sorted_s = s;
+            std::sort(sorted_s.begin(), sorted_s.end());
+
+            groups[sorted_s].push_back(s);
+        }
+
+        std::vector<words_t> result;
+        for (const auto [_, words] : groups) {
+            result.push_back(std::move(words));
+        }
+
+        return result;
+    }
+};