#1548. 【2022 正睿 NOIP 十连测 Day3】不

https://sjzezoj.com/submission/63066

S2OJ/1548/1548.cpp

@@ -0,0 +1,67 @@
+#include <iostream>
+#include <algorithm>
+#include <ctime>
+#include <random>
+#include <unordered_map>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 1e5 + 5;
+
+int n;
+long long w[N], ans;
+std::mt19937 rng(std::random_device{}());
+
+int random(int l, int r) {
+    return std::uniform_int_distribution<int>(l, r)(rng);
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n;
+
+    for (int i = 1; i <= n; i++) {
+        cin >> w[i];
+    }
+
+    while (clock() <= 0.6 * CLOCKS_PER_SEC) {
+        int p = random(1, n);
+
+        std::unordered_map<long long, int> cnt;
+        std::vector<long long> v;
+
+        for (int i = 1; i <= n; i++) {
+            cnt[std::__gcd(w[i], w[p])]++;
+        }
+
+        for (int i = 1; i <= w[p] / i; i++) {
+            if (w[p] % i == 0) {
+                v.push_back(i);
+                if ((w[p] / i) != i) v.push_back(w[p] / i);
+            }
+        }
+
+        for (long long x : v) {
+            int sum = 0;
+
+            for (long long y : v) {
+                if (y % x == 0) {
+                    sum += cnt[y];
+                }
+            }
+
+            if (sum >= (n + 1) / 2) {
+                ans = std::max(ans, x);
+            }
+        }
+    }
+
+    cout << ans << endl;
+
+    return 0;
+}