#160. 【模板】k 大异或和

https://sjzezoj.com/submission/64185

S2OJ/160/160.cpp

@@ -0,0 +1,70 @@
+#include <iostream>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 55;
+
+int n, m, cnt;
+unsigned long long x, k, a[N], p[N], ans;
+
+inline void insert(unsigned long long x) {
+    for (int i = 50; ~i; i--) {
+        if (x & (1ull << i)) {
+            if (a[i]) {
+                x ^= a[i];
+            } else {
+                for (int k = 0; k < i; k++) {
+                    if (x & (1ull << k)) x ^= a[k];
+                }
+
+                for (int k = i + 1; k <= 50; k++) {
+                    if (a[k] & (1ull << i)) a[k] ^= x;
+                }
+
+                a[i] = x;
+                return;
+            }
+        }
+    }
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n;
+
+    for (int i = 1; i <= n; i++) {
+        cin >> x;
+
+        insert(x);
+    }
+
+    for (int i = 0; i <= 50; i++) {
+        if (a[i]) p[cnt++] = a[i];
+    }
+
+    cin >> m;
+
+    while (m--) {
+        cin >> k;
+
+        if (cnt != n) k--;  // 非空
+
+        if (k >= (1ull << cnt)) {
+            cout << -1 << endl;
+        } else {
+            ans = 0;
+
+            for (int i = 0; i < cnt; i++) {
+                if (k & (1ull << i)) ans ^= p[i];
+            }
+
+            cout << ans << endl;
+        }
+    }
+
+    return 0;
+}