2017年省赛前最后一水---B题

问题 B: Prime
时间限制: 1 Sec 内存限制: 128 MB
提交: 166 解决: 78
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题目描述
Lucy give you a number n.
You should tell her the maximum prime no more than n.
输入
The first line of the input gives the number of test cases, T(1

#include <stdio.h>#include <stdlib.h>#include<map>#define N 10000000 #define Max 788066using namespace std;int prime[Max]={0};int num_prime = 0;bool *isNotPrime;void makePrime(){    for(int i = 2;i<N;i++)    {        if(!isNotPrime[i])            prime[num_prime++] = i;        for(int j = 0;j<num_prime && i*prime[j]<N;j++)        {            isNotPrime[i*prime[j]] = 1;            if(!(i%prime[j]))                break;          }    }    prime[num_prime++] = 10000019;}int find(int begin,int end,int temp){//  printf("%d %d %d\n",begin,end,temp);    int mid = begin+end;    mid/=2;    if(mid==0)        return 0;    if(prime[mid+1]>temp && prime[mid]<=temp)        return mid;    else if(prime[mid]<temp)            return find(mid+1,end,temp);    else        return find(begin,mid-1,temp);}int main(){    isNotPrime = (bool*)malloc(sizeof(bool)*N);    isNotPrime[0] = isNotPrime[1] = 1;    makePrime();    int n;    while(~scanf("%d",&n))    {        for(int k = 1;k<= n;k++)        {            int temp;            scanf("%d",&temp);            int index = find(0,num_prime,temp);        //  printf("%d\n",index);            printf("Case #%d: %d\n",k,prime[index]);        }    }    return 0;}/**************************************************************    Problem: 1012    User: T032    Language: C++    Result: 正确    Time:424 ms    Memory:13800 kb****************************************************************/