new file: P1404.cpp

P1404.cpp

@@ -0,0 +1,34 @@
+// 102
+// https://www.luogu.com.cn/article/42ly2wrn
+#include <bits/stdc++.h>
+#define int long long
+using namespace std;
+int n, l;
+int sum[100005];
+int q[100005];
+int t, h;
+double calc(int x, int y)
+{
+    return (0.0 + sum[y] - sum[x]) / (y - x);
+}
+signed main()
+{
+    scanf("%lld%lld", &n, &l);
+    for (int i = 1, x; i <= n; ++i)
+        scanf("%lld", &x), sum[i] = sum[i - 1] + x;
+    double ans = 0;
+    for (int i = l; i <= n; ++i) // lp
+    {
+        while (t - h >= 2 && calc(i - l, q[t - 1]) < calc(i - l, q[t - 2]))
+            t--;
+        q[t++] = i - l;
+        while (t - h >= 2 && calc(i, q[h]) < calc(i, q[h + 1]))
+            h++;
+        ans = max(ans, calc(i, q[h]));
+    }
+    printf("%lld\n", (long long)floor(1000 * ans));
+    return 0;
+}
+/*
+连续子序列平均值就转化为S-x平面上的斜率：avg(x,y)=(S(y)-s(x-1))/(y-x+1)
+*/