hdu 2138 How many prime numbers (素數判定），hdu2138

hdu 2138 How many prime numbers (素數判定），hdu2138

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 DescriptionGive you a lot of positive integers, just to find out how many prime numbers there are.

InputThere 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 32 3 4

Sample Output 2

Authorwangye

SourceHDU 2007-11 Programming Contest_WarmUp

解題思路：直接判定是否為素數即可。

AC代碼：

#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 0x7fffffffbool isprim(int n){              //判斷是否為素數    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;               //計數        while(n--){            scanf("%d", &x);            if(isprim(x)) ans ++;        }        printf("%d\n", ans);    }    return 0;}