ZOJ 3785 11th省赛 J What day is that day?【打表找规律】

题目链接

http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemId=5272

思路

就是说今天是星期六，问11+22+33+44+...nn天后是星期几。
打个表找规律吧，暴力查找下发现循环节是294。
比赛时没往这方面想，以为是递推关系，然后T了无数遍最后还是没做出来，唉总归是题目做的太少了。

以下是打表+暴力找循环节的代码：

#include <bits/stdc++.h>using namespace std;int a[1000000+100],p=0;int main(){    //freopen("out.txt","w",stdout);    int sum=0;    for(int i=1 ; i<=10000 ; ++i)    {        int fac=1;        for(int j=0 ; j<i ; ++j)        {            fac*=i;            fac%=7;        }        sum+=fac;        sum%=7;        int ans[]={6,0,1,2,3,4,5};        //printf(",%d",ans[sum]);        a[p++]=ans[sum];    }    for(int r=2 ; r<=1000 ; ++r)    {        bool flag=1;        for(int i=0 ; i<r ; ++i)        {            if(a[i]!=a[i+r])            {                flag=0;                break;            }        }        if(flag)printf("success!!!!::%d\n",r);    }    return 0;}

AC代码

#include <bits/stdc++.h>using namespace std;int a[]={-1,0,4,3,0,3,4,4,5,6,3,5,6,5,5,6,1,6,0,5,6,6,0,4,5,2,6,5,5,6,0,3,5,4,5,5,6,1,3,4,6,5,5,6,3,2,6,2,3,3,4,5,2,4,5,4,4,5,0,5,6,4,5,5,6,3,4,1,5,4,4,5,6,2,4,3,4,4,5,0,2,3,5,4,4,5,2,1,5,1,2,2,3,4,1,3,4,3,3,4,6,4,5,3,4,4,5,2,3,0,4,3,3,4,5,1,3,2,3,3,4,6,1,2,4,3,3,4,1,0,4,0,1,1,2,3,0,2,3,2,2,3,5,3,4,2,3,3,4,1,2,6,3,2,2,3,4,0,2,1,2,2,3,5,0,1,3,2,2,3,0,6,3,6,0,0,1,2,6,1,2,1,1,2,4,2,3,1,2,2,3,0,1,5,2,1,1,2,3,6,1,0,1,1,2,4,6,0,2,1,1,2,6,5,2,5,6,6,0,1,5,0,1,0,0,1,3,1,2,0,1,1,2,6,0,4,1,0,0,1,2,5,0,6,0,0,1,3,5,6,1,0,0,1,5,4,1,4,5,5,6,0,4,6,0,6,6,0,2,0,1,6,0,0,1,5,6,3,0,6,6,0,1,4,6,5,6,6,0,2,4,5,0,6,6};int main(){    int T;    scanf("%d",&T);    while(T--)    {        int n;        scanf("%d",&n);        char s[][50]={"Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday"};        printf("%s\n",s[a[n%294==0?294:n%294]]);        //printf("%d\n",ans);    }    return 0;}