another fix

Author: lrvideckis

library/math/matrix_related/row_reduce.hpp

@@ -1,5 +1,5 @@
 #pragma once
-#include "../mod_int.hpp"
+#include "../mod_division.hpp"
 //! @code
 //!   auto [rank, det] = row_reduce(mat, cols);
 //! @endcode
@@ -8,28 +8,31 @@
 //!   affected by row operations
 //! @time O(n * m * min(cols, n))
 //! @space O(1)
-pair<int, mint> row_reduce(vector<vector<mint>>& mat,
+pair<int, int> row_reduce(vector<vector<int>>& mat,
   int cols) {
   int n = sz(mat), m = sz(mat[0]), rank = 0;
-  mint det = 1;
+  int det = 1;
   for (int col = 0; col < cols && rank < n; col++) {
     auto it = find_if(rank + all(mat),
-      [&](auto& v) { return v[col].x; });
+      [&](auto& v) { return v[col]; });
     if (it == end(mat)) {
       det = 0;
       continue;
     }
     if (it != begin(mat) + rank) {
-      det = mint(0) - det;
+      det = (mod - det) % mod;
       iter_swap(begin(mat) + rank, it);
     }
-    det = det * mat[rank][col];
-    mint a_inv = mint(1) / mat[rank][col];
-    for (mint& num : mat[rank]) num = num * a_inv;
-    rep(i, 0, n) if (i != rank && mat[i][col].x != 0) {
-      mint num = mat[i][col];
+    det = 1LL * det * mat[rank][col] % mod;
+    int a_inv = mod_div(1, mat[rank][col]);
+    for (int& num : mat[rank])
+      num = 1LL * num * a_inv % mod;
+    rep(i, 0, n) if (i != rank && mat[i][col] != 0) {
+      int num = mat[i][col];
       rep(j, 0, m) mat[i][j] =
-        mat[i][j] - mat[rank][j] * num;
+        ((mat[i][j] - 1LL * mat[rank][j] * num) % mod +
+          mod) %
+        mod;
     }
     rank++;
   }

library/math/matrix_related/solve_linear_mod.hpp

@@ -11,22 +11,21 @@
 //! @time O(n * m * min(n, m))
 //! @space O(m)
 struct solve_linear_mod {
-  int rank;
-  mint det;
-  vector<mint> sol;
-  solve_linear_mod(vector<vector<mint>>& mat,
-    const vector<mint>& rhs) {
+  int rank, det;
+  vector<int> sol;
+  solve_linear_mod(vector<vector<int>>& mat,
+    const vector<int>& rhs) {
     int n = sz(mat), m = sz(mat[0]);
     rep(i, 0, n) mat[i].push_back(rhs[i]);
     tie(rank, det) = row_reduce(mat, m);
     if (any_of(rank + all(mat),
-          [](auto& v) { return v.back().x; })) {
+          [](vi& v) { return v.back(); })) {
       return;
     }
     sol.resize(m);
     int j = 0;
-    for_each(begin(mat), begin(mat) + rank, [&](auto& v) {
-      while (v[j].x == 0) j++;
+    for_each(begin(mat), begin(mat) + rank, [&](vi& v) {
+      while (!v[j]) j++;
       sol[j] = v.back();
     });
   }

tests/library_checker_aizu_tests/math/solve_linear_mod.test.cpp

@@ -6,33 +6,32 @@ int main() {
   cin.tie(0)->sync_with_stdio(0);
   int n, m;
   cin >> n >> m;
-  vector<vector<mint>> mat(n, vector<mint>(m));
+  vector<vector<int>> mat(n, vector<int>(m));
   for (int i = 0; i < n; i++)
-    for (int j = 0; j < m; j++) cin >> mat[i][j].x;
-  vector<mint> b(n);
-  for (int i = 0; i < n; i++) cin >> b[i].x;
+    for (int j = 0; j < m; j++) cin >> mat[i][j];
+  vector<int> b(n);
+  for (int i = 0; i < n; i++) cin >> b[i];
   solve_linear_mod info(mat, b);
   assert(info.rank <= min(n, m));
   if (empty(info.sol)) {
     cout << -1 << '\n';
     return 0;
   }
   cout << m - info.rank << '\n';
-  for (auto val : info.sol) cout << val.x << " ";
+  for (int val : info.sol) cout << val << " ";
   cout << '\n';
   vector<int> pivot(m, -1);
   for (int i = 0, j = 0; i < info.rank; i++) {
-    while (mat[i][j].x == 0) j++;
+    while (mat[i][j] == 0) j++;
     pivot[j] = i;
   }
   for (int j = 0; j < m; j++)
     if (pivot[j] == -1) {
-      vector<mint> x(m, 0);
-      x[j] = -1;
-      assert(0 <= x[j].x && x[j].x < mod);
+      vector<int> x(m, 0);
+      x[j] = mod - 1;
       for (int k = 0; k < j; k++)
         if (pivot[k] != -1) x[k] = mat[pivot[k]][j];
-      for (int k = 0; k < m; k++) cout << x[k].x << " ";
+      for (int k = 0; k < m; k++) cout << x[k] << " ";
       cout << '\n';
     }
   return 0;