split "cosets" and "solver" data. "solver.cpp" now only for solution logic.

include/cosets.h

@@ -0,0 +1,33 @@
+#pragma once
+
+#include "groups.h"
+#include <vector>
+
+struct Cosets {
+    int ngens;
+    std::vector<int> data;
+    int len;
+
+    Cosets(int ngens, const std::vector<int> &data);
+
+    void add_row();
+
+    void put(int coset, int gen, int target);
+
+    void put(int idx, int target);
+
+    [[nodiscard]] int get(int coset, int gen) const;
+
+    [[nodiscard]] int get(int idx) const;
+};
+
+struct RelTable {
+    int gens[2]{};
+    int mult;
+    std::vector<int *> lst_ptr;
+    std::vector<int> gen;
+
+    explicit RelTable(tc::Mult m);
+
+    int add_row();
+};