cpp: add “1239. Maximum Length of a Concatenated String with Unique Characters”

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

cpp/maximum-length-of-a-concatenated-string-with-unique-characters.cpp

@@ -0,0 +1,66 @@
+#include <bit>
+#include <cassert>
+#include <cstdint>
+#include <iostream>
+#include <string>
+#include <vector>
+
+class Solution {
+    static auto construct_sets(const std::vector<std::string> &arr)
+        -> std::vector<uint32_t> {
+        std::vector<std::uint32_t> sets;
+
+        for (const auto &word : arr) {
+            std::uint32_t w = 0;
+
+            for (char c : word) {
+                auto mask = 1 << (c - 'a');
+
+                if ((w & mask) != 0) {
+                    w = 0;
+                    break;
+                }
+                w |= mask;
+            }
+
+            sets.push_back(w);
+        }
+
+        return sets;
+    }
+
+    static auto find_solution(const std::vector<std::uint32_t> &words,
+                              std::size_t i, std::uint32_t w) -> int {
+        if (i == words.size()) {
+            return std::popcount(w);
+        }
+
+        auto found_solution = find_solution(words, i + 1, w);
+        if ((words[i] & w) == 0) {
+            found_solution = std::max(
+                found_solution, find_solution(words, i + 1, w | words[i]));
+        }
+
+        return found_solution;
+    }
+
+  public:
+    int maxLength(const std::vector<std::string> &arr) {
+        auto sets = construct_sets(arr);
+        return find_solution(sets, 0u, 0u);
+    }
+};
+
+int main() {
+    Solution s;
+
+    assert(s.maxLength(std::vector{std::string{"un"}, std::string{"iq"},
+                                   std::string{"ue"}}) == 4);
+    assert(s.maxLength(std::vector{std::string{"cha"}, std::string{"r"},
+                                   std::string{"act"}, std::string{"ers"}}) ==
+           6);
+    assert(s.maxLength(
+               std::vector{std::string{"abcdefghijklmnopqrstuvwxyz"}}) == 26);
+
+    return 0;
+}