HDU - 2973 - YAPTCHA
先上题目:
YAPTCHA
Time Limit: 10000/5000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 463 Accepted Submission(s): 280
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.
first line contains the number of queries t (t <= 10^6). Each query
consist of one natural number n (1 <= n <= 10^6).
1
2
3
4
5
6
7
8
9
10
100
1000
10000
#include <stdio.h>
#include <string.h>
#define MAX 1000110
using namespace std; bool pri[MAX*];
int ans[MAX]; void dedeal()
{
long long i,j,n;
n=(MAX-)*;
memset(pri,,sizeof(pri));
pri[]=pri[]=;
for(i=;i<=n;i++)
{
if(!pri[i])
for(j=i*i;j<=n;j+=i) pri[j]=;
}
} void deal()
{
int i,n;
n=(MAX-);
memset(ans,,sizeof(ans));
for(i=;i<=n;i++)
{
if(!pri[*i+])
ans[i]=ans[i-]+;
else ans[i]=ans[i-];
}
} int main()
{
int n,t;
//freopen("data.txt","r",stdin);
dedeal();
deal();
scanf("%d",&t);
while(t--)
{
scanf("%d\n",&n);
printf("%d\n",ans[n]);
}
return ;
}
2973
提速版
#include <iostream>
#include <string.h>
#include <stdio.h>
#define MAX 1000110
using namespace std ;
bool pri[] ;
int ans[] ; void dedeal()
{
long long i,j,n;
n=(MAX-)*;
memset(pri,,sizeof(pri));
pri[]=pri[]=;
for(i=;i<=n;i++)
{
if(!pri[i])
for(j=i*i;j<=n;j+=i) pri[j]=;
}
} void deal()
{
int i,n;
n=(MAX-);
memset(ans,,sizeof(ans));
for(i=;i<=n;i++)
{
if(!pri[*i+])
ans[i]=ans[i-]+;
else ans[i]=ans[i-];
}
} inline bool scan_d(int &num)
{
char in;bool IsN=false;
in=getchar();
if(in==EOF) return false;
while(in!='-'&&(in<''||in>'')) in=getchar();
if(in=='-'){ IsN=true;num=;}
else num=in-'';
while(in=getchar(),in>=''&&in<=''){
num*=,num+=in-'';
}
if(IsN) num=-num;
return true;
} void print_f(int x){
if(x==)return;
print_f(x/);
putchar(x%+'');
}
int main()
{
//freopen("data.txt","r",stdin);
int t ;
dedeal();
deal();
scan_d(t) ;
while(t--)
{
int n ;
scan_d(n) ;
if(n==)
putchar('') ;
else
print_f(ans[n]) ;
putchar('\n') ;
}
return ;
}
2973
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