1830. 开关问题

http://poj.org/showsource?solution_id=23487503

POJ/1830/1830.cpp

@@ -0,0 +1,80 @@
+#include <cstring>
+#include <iostream>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 35;
+
+int t, n, a[N][N];
+
+int gauss() {
+    int r, c;
+    for (r = c = 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++;
+    }
+
+    int res = 1;
+
+    if (r <= n) {
+        for (int i = r; i <= n; i++) {
+            if (a[i][n + 1]) return -1;
+            res <<= 1;
+        }
+    }
+
+    return res;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+
+    cin >> t;
+
+    while (t--) {
+        memset(a, 0x00, sizeof(a));
+
+        cin >> n;
+
+        for (int i = 1; i <= n; i++) {
+            cin >> a[i][n + 1];
+        }
+
+        for (int i = 1, x; i <= n; i++) {
+            cin >> x;
+            a[i][n + 1] ^= x;
+            a[i][i] = 1;
+        }
+
+        int x, y;
+        while (cin >> x >> y, x || y) a[y][x] = 1;
+
+        int r = gauss();
+
+        if (r == -1) {
+            cout << "Oh,it's impossible~!!" << endl;
+        } else {
+            cout << r << endl;
+        }
+    }
+
+    return 0;
+}