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  • YAPTCHA(hdu2973)

    YAPTCHA

    Time Limit: 10000/5000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
    Total Submission(s): 862    Accepted Submission(s): 452


    Problem Description
    The math department has been having problems lately. Due to immense amount of unsolicited automated programs which were crawling across their pages, they decided to put Yet-Another-Public-Turing-Test-to-Tell-Computers-and-Humans-Apart on their webpages. In short, to get access to their scientific papers, one have to prove yourself eligible and worthy, i.e. solve a mathematic riddle.


    However, the test turned out difficult for some math PhD students and even for some professors. Therefore, the math department wants to write a helper program which solves this task (it is not irrational, as they are going to make money on selling the program).

    The task that is presented to anyone visiting the start page of the math department is as follows: given a natural n, compute

    where [x] denotes the largest integer not greater than x.
     
    Input
    The first line contains the number of queries t (t <= 10^6). Each query consist of one natural number n (1 <= n <= 10^6).
     
    Output
    For each n given in the input output the value of Sn.
     
    Sample Input
    13 1 2 3 4 5 6 7 8 9 10 100 1000 10000
     
    Sample Output
    0 1 1 2 2 2 2 3 3 4 28 207 1609
    思路:素数打表+威尔逊定理;
     1 #include<stdio.h>
     2 #include<algorithm>
     3 #include<iostream>
     4 #include<string.h>
     5 #include<queue>
     6 #include<set>
     7 #include<math.h>
     8 using namespace std;
     9 typedef long long LL;
    10 bool prime[4000000];
    11 int sum[4000009];
    12 int main(void)
    13 {
    14         int n;
    15         memset(prime,0,sizeof(prime));
    16         for(int i = 2; i < 3000; i++)
    17         {
    18                 if(!prime[i])
    19                         for(int j = i; (i*j) <=4000007 ; j++)
    20                         {
    21                                 prime[i*j] = true;
    22                         }
    23         }
    24         memset(sum,0,sizeof(sum));
    25         for(int i = 1; i <= 1000000; i++)
    26         {
    27                 if(!prime[3*i+7])
    28                         sum[i] = sum[i-1] + 1;
    29                 else sum[i] = sum[i-1];
    30         }
    31         scanf("%d",&n);
    32         while(n--)
    33         {
    34                 int ask ;
    35                 scanf("%d",&ask);
    36                 printf("%d
    ",sum[ask]);
    37         }
    38         return 0;
    39 }
    油!油!you@
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  • 原文地址:https://www.cnblogs.com/zzuli2sjy/p/5876723.html
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