#1909. 染色

https://sjzezoj.com/submission/69017

S2OJ/1909/1909.cpp

@@ -0,0 +1,96 @@
+#include <iostream>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 2005;
+
+int n, a[N][N];
+
+int gauss() {
+    int c, r;
+
+    for (c = r = 1; c <= n; c++) {
+        int t = r;
+
+        for (int i = r; i <= n; i++) {
+            if (a[i][c]) t = i;
+        }
+
+        if (!a[t][c]) continue;
+
+        std::swap(a[t], a[r]);
+
+        for (int i = r + 1; i <= n; i++) {
+            if (a[i][c]) {
+                for (int j = n + 1; j >= c; j--) {
+                    a[i][j] ^= a[r][j];
+                }
+            }
+        }
+
+        r++;
+    }
+
+    if (r <= n) {
+        for (int i = r; i <= n; i++) {
+            if (a[i][n + 1]) {
+                return -1;
+            }
+        }
+    }
+
+    for (int i = n; i; i--) {
+        for (int j = i + 1; j <= n; j++) {
+            a[i][n + 1] ^= a[i][j] & a[j][n + 1];
+        }
+    }
+
+    return 0;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n;
+
+    for (int i = 1, k; i <= n; i++) {
+        cin >> k;
+
+        for (int j = 1, x; j <= k; j++) {
+            cin >> x;
+
+            a[i][x] = 1;
+        }
+
+        if (k % 2) {
+            a[i][i] = 1;
+            a[i][n + 1] = 1;
+        }
+    }
+
+    if (gauss() != 0) {
+        cout << -1 << endl;
+    } else {
+        std::vector<int> ans;
+
+        for (int i = 1; i <= n; i++) {
+            if (a[i][n + 1]) {
+                ans.push_back(i);
+            }
+        }
+
+        cout << ans.size() << endl;
+
+        for (int x : ans) {
+            cout << x << ' ';
+        }
+
+        cout << endl;
+    }
+
+    return 0;
+}