SHOI 2002 百事世界杯之旅 | 概率论

Posted 2020-10-25 milky-w

题目：SHOI 2002

若当前已经有了 x 种，再买一个买到不一样的概率为 (n-x)/n，要使这个概率变成 1，则至少再买 n/(n-x) 瓶。

 1 #include <cstdio>
 2 #include <string>
 3 
 4 long long max(long long x, long long y) {
 5     return y < x ? x : y;
 6 }
 7 
 8 long long gcd(long long x, long long y) {
 9     return y ? gcd(y, x % y) : x;
10 }
11 
12 int main() {
13     int n; scanf("%d", &n); long long x = 1, y = 1, t;
14     for (register int i = 2; i <= n; ++ i) {
15         t = y * i / gcd(y, i), x = t / y * x + t / i, y = t;
16     }
17     x *= n, t = gcd(x, y), x /= t, y /= t, t = x / y, x %= y;
18     if (x == 0) {
19         printf("%lld\n", t);
20     } else {
21         int a = 0, b = 0; long long r = t;
22         while (r) r /= 10, ++ a;
23         for (register int i = 1; i <= a; ++ i) putchar(‘ ‘);
24         printf("%lld\n%lld", x, t);
25         r = max(x, y);
26         while (r) r /= 10, ++ b;
27         for (register int i = 1; i <= b; ++ i) putchar(‘-‘);
28         puts("");
29         for (register int i = 1; i <= a; ++ i) putchar(‘ ‘);
30         printf("%lld\n", y);
31     }
32     return 0;
33 }