zoj3785 What day is that day?
It's Saturday today, what day is it after 11 + 22 + 33 + ... + NN days?
Input
There are multiple test cases. The first line of input contains an integer T indicating the number of test cases. For each test case:
There is only one line containing one integer N (1 <= N <= 1000000000).
Output
For each test case, output one string indicating the day of week.
Sample Input
2
1
2
Sample Output
Sunday
Thursday
Hint
A week consists of Sunday, Monday, Tuesday, Wednesday, Thursday, Friday and Saturday.
题目大意:今天是星期六,输入n,问11 + 22 + 33 + ... + NN 天后是星期几?
思路:因为n是10亿,解法必定是数学方法或者找规律。注意到7是素数,所以可以使用费马小定理进行简化。即当p是素数是,a^(p-1) mod p=1,简化后发现每42个数就会出现一个循环,得数mod7=6。所以求解过程就是先求出n由几个42组成,对于42取余的剩下的部分就可以直接模拟做了。
/*
* Author: Joshua
* Created Time: 2014/5/17 13:18:55
* File Name: j.cpp
*/
#include<cstdio>
#include<iostream>
#include<cstring>
#include<cstdlib>
#include<cmath>
#include<algorithm>
#include<string>
#include<map>
#include<set>
#include<vector>
#include<queue>
#include<stack>
#include<ctime>
#include<utility>
#define M0(x) memset(x, 0, sizeof(x))
#define MP make_pair
#define Fi first
#define Se second
#define rep(i, a, b) for (int i = (a); i <= (b); ++i)
#define red(i, a, b) for (int i = (a); i >= (b); --i)
#define PB push_back
#define Inf 0x3fffffff
#define eps 1e-8
typedef long long LL;
using namespace std; string ans[]={"Saturday","Sunday","Monday","Tuesday","Wednesday","Thursday","Friday"}; void solve()
{
int n,m,t=,temp;
scanf("%d",&n);
m=n/;
t=(t+m*)%;
for (int i=;i<=n%;i++)
{
temp=;
for (int j=;j<=i;j++)
temp=(temp*i)%;
t=(t+temp)%;
}
cout<<ans[t]<<endl;
}
int main()
{
int tt;
scanf("%d",&tt);
while (tt)
{
tt--;
solve();
}
return ;
}
许久没写了,代码太丑,大家凑合着看。。。
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