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hdu 2138 How many prime numbers (素数判定）
How many prime numbers |
| Time Limit: 3000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others) |
| Total Submission(s): 8205 Accepted Submission(s): 2642 |
Problem Description Give you a lot of positive integers, just to find out how many prime numbers there are. |
Input There are a lot of cases. In each case, there is an integer N representing the number of integers to find. Each integer won’t exceed 32-bit signed integer, and each of them won’t be less than 2. |
Output For each case, print the number of prime numbers you have found out. |
Sample Input 3 2 3 4 |
Sample Output 2 |
Author wangye |
Source HDU 2007-11 Programming Contest_WarmUp |
解题思路：直接判定是否为素数即可。
AC代码：
#include <stdio.h>
#include <string.h>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <math.h>
#include <stdlib.h>
#include <time.h>
using namespace std;
#define INF 0x7fffffff
bool isprim(int n){ //判断是否为素数
for(int i=2; i<=(double)sqrt((double)n); i++){
if(n%i == 0) return false;
}
return true;
}
int main()
{
#ifdef sxk
freopen("in.txt","r",stdin);
#endif
int n, x, ans;
while(scanf("%d",&n)!=EOF)
{
ans = 0; //计数
while(n--){
scanf("%d", &x);
if(isprim(x)) ans ++;
}
printf("%d\n", ans);
}
return 0;
}hdu 2138 How many prime numbers (素数判定）
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