update

src/8/21/strexpect.cpp

@@ -0,0 +1,14 @@
+/*
+假设一个随机数生成器每次随机一个数[1,n]，形成一个无限长的字符串s，
+给定一个长度为m的数，那么第一次在s中出现位置的期望是多少
+
+n=2 12 的位置
+e[1]=1/2*1+1/2*(e[1]+1)
+
+
+
+*/
+
+int main(){
+
+}

src/8/22/P1297.cpp

@@ -0,0 +1,29 @@
+#include <algorithm>
+#include <cstdio>
+#include <iostream>
+#include <vector>
+
+#define long long long
+
+using namespace std;
+
+int main() {
+    ios_base::sync_with_stdio(false);
+    cin.tie(NULL);
+    int n;
+    long A, B, C;
+    vector<long> a(10000001);
+    scanf("%d%lld%lld%lld%ld", &n, &A, &B, &C, &a[1]);
+    for (int i = 2; i <= n; ++i) {
+        a[i] = (a[i - 1] * A + B) % 100000001;
+    }
+    for (int i = 1; i <= n; ++i) {
+        a[i] = a[i] % C + 1;
+    }
+    double exp = 0.0;
+    for (int i = 2; i <= n; ++i) {
+        exp += (double)min(a[i - 1], a[i]) / (double)(a[i - 1] * a[i]);
+    }
+    exp += (double)min(a[n], a[1]) / (double)(a[n] * a[1]);
+    printf("%.3f\n", exp);
+}