BZOJ1053:[HAOI2007]反素数——题解

http://www.lydsy.com/JudgeOnline/problem.php?id=1053

对于任何正整数x,其约数的个数记作g(x)。例如g(1)=1、g(6)=4。如果某个正整数x满足:g(x)>g(i) 0<i<x,则称x为反质数。例如,整数1,2,4,6等都是反质数。现在给定一个数N,你能求出不超过N的最大的反质数么?

题意可以改成:求1~n内g(i)最大i最小的i。

网上有人说可以爆搜。

但是更暴力的方法就是打表啦,n=2e9不就一分钟的事吗……

#include<cstdio>
#include<iostream>
#include<queue>
#include<cstring>
#include<algorithm>
#include<cctype>
using namespace std;
int p[500]={1,2,4,6,12,24,36,48,60,120,180,240,360,720,840,1260,1680,2520,5040,7560,10080,15120,20160,25200,27720,45360,50400,55440,83160,110880,166320,221760,277200,332640,498960,554400,665280,720720,1081080,1441440,2162160,2882880,3603600,4324320,6486480,7207200,8648640,10810800,14414400,17297280,21621600,32432400,36756720,43243200,61261200,73513440,110270160,122522400,147026880,183783600,245044800,294053760,367567200,551350800,698377680,735134400,1102701600,1396755360,2001000000};
int main(){
    int n;
    scanf("%d",&n);
    for(int i=0;i<500;i++){
    if(p[i]>n){
        printf("%d\n",p[i-1]);
        return 0;
    }
    }
}

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 +本文作者:luyouqi233。               +

 +欢迎访问我的博客:http://www.cnblogs.com/luyouqi233/+

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posted @ 2018-02-28 16:16  luyouqi233  阅读(260)  评论(0编辑  收藏  举报