feat: levenshtein_distance() function (#511)

Author: benthevining

libutil/include/libutil/Strings.hpp

@@ -130,6 +130,10 @@ void write_integer(
  */
 [[nodiscard]] auto words_view(string_view text);
 
+/** Computes the Levenshtein distance between the two strings. */
+[[nodiscard, gnu::const]] auto levenshtein_distance(
+    string_view first, string_view second) -> size_t;
+
 /// @}
 
 /*

libutil/src/Strings.cpp

@@ -23,6 +23,7 @@
 #include <ranges>
 #include <string>
 #include <string_view>
+#include <vector>
 
 namespace {
 
@@ -150,4 +151,31 @@ auto split_at_first_space_or_newline(const string_view input) -> StringViewPair
     };
 }
 
+auto levenshtein_distance(
+    const string_view first, const string_view second) -> size_t
+{
+    const auto size_a = first.size();
+    const auto size_b = second.size();
+
+    auto distances = std::views::iota(0uz, size_b + 1uz)
+                   | std::ranges::to<std::vector>();
+
+    for (auto i = 0uz; i < size_a; ++i) {
+        auto prevDist = 0uz;
+
+        for (auto j = 0uz; j < size_b; ++j) {
+            const auto next = distances.at(j + 1uz);
+
+            const auto dist = std::exchange(prevDist, next)
+                            + (first.at(i) == second.at(j) ? 0uz : 1uz);
+
+            distances.at(j + 1uz) = std::min({ dist,
+                distances.at(j) + 1uz,
+                next + 1uz });
+        }
+    }
+
+    return distances.at(size_b);
+}
+
 } // namespace util::strings

tests/unit/libutil/Strings.cpp

@@ -219,3 +219,20 @@ TEST_CASE("Strings - words_view()", TAGS)
         REQUIRE(words.back() == "456");
     }
 }
+
+TEST_CASE("Strings - Levenshtein distance", TAGS)
+{
+    using util::strings::levenshtein_distance;
+
+    REQUIRE(
+        levenshtein_distance("kitten", "sitting") == 3uz);
+
+    REQUIRE(
+        levenshtein_distance("corporate", "cooperation") == 5uz);
+
+    REQUIRE(
+        levenshtein_distance("123", { }) == 0uz);
+
+    REQUIRE(
+        levenshtein_distance({ }, { }) == 0uz);
+}