P2503 [HAOI2006]均分数据

https://www.luogu.com.cn/record/87697641

Luogu/P2503/P2503.cpp

@@ -0,0 +1,45 @@
+#include <iostream>
+#include <algorithm>
+#include <cmath>
+#include <iomanip>
+#include <numeric>
+#include <random>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    int n, m;
+    double ans = 1e9;
+    std::mt19937 rng(std::random_device{}());
+
+    cin >> n >> m;
+
+    std::vector<int> a(n);
+
+    for (int& x : a) cin >> x;
+
+    for (int i = 0; i < 1000000; i++) {
+        std::vector<int> b(m);
+
+        std::shuffle(a.begin(), a.end(), rng);
+
+        for (int x : a) {
+            *std::min_element(b.begin(), b.end()) += x;
+        }
+
+        double avg = static_cast<double>(std::accumulate(b.begin(), b.end(), 0)) / m;
+        double variance = std::sqrt(std::accumulate(b.begin(), b.end(), 0.0, [&](double sum, int x) { return sum + std::pow(avg - x, 2); }) / m);
+
+        ans = std::min(ans, variance);
+    }
+
+    cout << std::fixed << std::setprecision(2) << ans << endl;
+
+    return 0;
+}