Test for system of linear equations mod 2 + use C++23

Author: adamant-pwn

.verify-helper/config.toml

@@ -1,3 +1,3 @@
 [[languages.cpp.environments]]
 CXX = "g++"
-CXXFLAGS = ["-std=c++20", "-Wall", "-Wextra", "-O2", "-march=native"]
+CXXFLAGS = ["-std=c++23", "-Wall", "-Wextra", "-O2", "-march=native"]

verify/data_structures/bitpack/system_mod_2.test.cpp

@@ -0,0 +1,75 @@
+// @brief System of Linear Equations (Mod 2)
+#define PROBLEM "https://judge.yosupo.jp/problem/system_of_linear_equations_mod_2"
+#pragma GCC optimize("Ofast,unroll-loops")
+#include "cp-algo/data_structures/bitpack.hpp"
+#include <bits/stdc++.h>
+
+using namespace std;
+using cp_algo::data_structures::bitpack;
+
+const int maxn = (1 << 12) + 1;
+bitpack<maxn> a[maxn];
+
+void solve() {
+    int n, m;
+    cin >> n >> m;
+    string As[n];
+    for(int i = 0; i < n; i++) {
+        cin >> As[i];
+    }
+    string bs;
+    cin >> bs;
+    for(int i = 0; i < n; i++) {
+        As[i] += bs[i];
+        a[i] = As[i];
+    }
+    vector<int> lead(n);
+    auto vars = views::iota(0, m + 1);
+    set<int> free(begin(vars), end(vars));
+    for(int i = 0; i < n; i++) {
+        for(int j = 0; j < i; j++) {
+            if(a[i][lead[j]]) {
+                a[i].xor_hint(a[j], lead[j]);
+            }
+        }
+        lead[i] = a[i].ctz();
+        if(lead[i] == m) {
+            cout << -1 << "\n";
+            return;
+        }
+        if(lead[i] > m) {
+            continue;
+        }
+        free.erase(lead[i]);
+        for(int j = 0; j < i; j++) {
+            if(a[j][lead[i]]) {
+                a[j].xor_hint(a[i], lead[i]);
+            }
+        }
+    }
+    bitpack<maxn> x[maxn];
+    for(auto [j, pj]: views::enumerate(free)) {
+        x[j].set(pj);
+        for(int i = 0; i < n; i++) {
+            if(lead[i] < m && a[i][pj]) {
+                x[j].set(lead[i]);
+            }
+        }
+    }
+    int rk = size(free) - 1;
+    swap(x[0], x[rk]);
+    cout << rk << "\n";
+    for(int i = 0; i <= rk; i++) {
+        cout << x[i].to_string().substr(0, m) << "\n";
+    }
+}
+
+signed main() {
+    //freopen("input.txt", "r", stdin);
+    ios::sync_with_stdio(0);
+    cin.tie(0);
+    int t = 1;
+    while(t--) {
+        solve();
+    }
+}