Рекурсивно решение на ход на коня

lectures/1/horse/CMakeLists.txt

@@ -4,7 +4,7 @@ project(horse VERSION 0.1.0)
 include(CTest)
 enable_testing()
 
-add_executable(horse main.cpp recursive_horsewalker.cpp)
+add_executable(horse main.cpp horsewalker.cpp recursive_horsewalker.cpp)
 include_directories(../common ../stack)
 
 set(CPACK_PROJECT_NAME ${PROJECT_NAME})

lectures/1/horse/horse_tests.hpp

@@ -1,7 +1,43 @@
 #include "recursive_horsewalker.hpp"
 
+TEST_CASE_TEMPLATE("Никъде не можем да стигнем от невалидна стартова позиция",
+                    AnyHorseWalker, RecursiveHorseWalker) {
+    AnyHorseWalker horseWalker(4);
+    CHECK_FALSE(horseWalker.existsWalk({-1, 0}, {3, 3}));
+}
+
+TEST_CASE_TEMPLATE("Не можем да стигнем до невалидна крайна позиция",
+                    AnyHorseWalker, RecursiveHorseWalker) {
+    AnyHorseWalker horseWalker(4);
+    CHECK_FALSE(horseWalker.existsWalk({0, 0}, {3, 5}));
+}
+
+TEST_CASE_TEMPLATE("Началната и крайната позиция съвпадат",
+                    AnyHorseWalker, RecursiveHorseWalker) {
+    AnyHorseWalker horseWalker(4);
+    CHECK(horseWalker.existsWalk({0, 0}, {0, 0}));
+}
+
 TEST_CASE_TEMPLATE("На дъска 4x4 можем да стигнем от (0,0) до (3,3)",
                     AnyHorseWalker, RecursiveHorseWalker) {
     AnyHorseWalker horseWalker(4);
     CHECK(horseWalker.existsWalk({0, 0}, {3, 3}));
+}
+
+TEST_CASE_TEMPLATE("На дъска 4x4 можем да стигнем от (0,0) до (2,2)",
+                    AnyHorseWalker, RecursiveHorseWalker) {
+    AnyHorseWalker horseWalker(4);
+    CHECK(horseWalker.existsWalk({0, 0}, {2, 2}));
+}
+
+TEST_CASE_TEMPLATE("На дъска 4x4 можем да стигнем от (0,0) до (0,1)",
+                    AnyHorseWalker, RecursiveHorseWalker) {
+    AnyHorseWalker horseWalker(4);
+    CHECK(horseWalker.existsWalk({0, 0}, {0, 1}));
+}
+
+TEST_CASE_TEMPLATE("На дъска 3x3 не можем да стигнем от (0,0) до (1,1)",
+                    AnyHorseWalker, RecursiveHorseWalker) {
+    AnyHorseWalker horseWalker(3);
+    CHECK_FALSE(horseWalker.existsWalk({0, 0}, {1, 1}));
 }

lectures/1/horse/horsewalker.cpp

@@ -0,0 +1,15 @@
+#include "horsewalker.hpp"
+
+HorseWalker::HorseWalker(size_t size) {
+    initBoard(size);
+}
+
+void HorseWalker::initBoard(size_t size) {
+    for(size_t i = 0; i < size; i++)
+        board.push_back(ChessRow(size));
+}
+
+bool HorseWalker::insideBoard(Position const& pos) const {
+    return pos.first >= 0  && pos.first < board.size() &&
+           pos.second >= 0 && pos.second < board.size();
+}

lectures/1/horse/horsewalker.hpp

@@ -1,12 +1,24 @@
 #ifndef __HORSE_WALKER
 #define __HORSE_WALKER
+#include <cstddef>
 #include <utility>
+#include <vector>
 
 using Position = std::pair<int, int>;
+// TODO: да се реализира чрез std::array
+using ChessRow   = std::vector<bool>;
+using ChessBoard = std::vector<ChessRow>;
 
 class HorseWalker {
+protected:
+    ChessBoard board;
+    void initBoard(size_t size);
+    bool insideBoard(Position const& pos) const;
 public:
-    virtual bool existsWalk(Position const& start, Position const& end) const = 0;
+    HorseWalker(size_t size = 8);
+
+    // проверява дали има разходка на коня от start до end
+    virtual bool existsWalk(Position const& start, Position const& end) = 0;
     virtual ~HorseWalker() {}
 };
 

lectures/1/horse/recursive_horsewalker.cpp

@@ -1,7 +1,24 @@
+#include <cmath>
 #include "recursive_horsewalker.hpp"
 
-RecursiveHorseWalker::RecursiveHorseWalker(size_t size) {}
+RecursiveHorseWalker::RecursiveHorseWalker(size_t size) : HorseWalker(size) {}
+
+bool RecursiveHorseWalker::existsWalk(Position const& start, Position const& end) {
+    if (!insideBoard(start) || !insideBoard(end) || board[start.first][start.second])
+        return false;
+
+    if (start == end)
+        return true;
+
+    board[start.first][start.second] = true;
+
+    for(int dx = -2; dx <= 2; dx++)
+        if (dx != 0)
+            for (int sign : {-1, 1}) {
+                int dy = sign * (3 - std::abs(dx));
+                if (existsWalk({start.first + dx, start.second + dy}, end))
+                    return true; 
+            }
 
-bool RecursiveHorseWalker::existsWalk(Position const& start, Position const& end) const {
     return false;
 }

lectures/1/horse/recursive_horsewalker.hpp

@@ -6,7 +6,7 @@
 class RecursiveHorseWalker : public HorseWalker {
 public:
     RecursiveHorseWalker(size_t size = 8);
-    bool existsWalk(Position const& start, Position const& end) const;
+    bool existsWalk(Position const& start, Position const& end);
 };
 
 #endif