Bestcoder #21&&hdoj 5139 Formula 【另类打表之分块】

Formula

Time Limit: 4000/2000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)

Total Submission(s): 155    Accepted Submission(s): 69

Problem Description

f(n)=(∏i=1nin−i+1)%1000000007
You are expected to write a program to calculate f(n) when a certain n is given.

 

Input

Multi test cases (about 100000), every case contains an integer n in a single line.
Please process to the end of file.

[Technical Specification]
1≤n≤10000000

 

Output

For each n，output f(n) in a single line.

 

Sample Input

2100

 

Sample Output

2148277692

 

题意：计算i从1~n的i^（n-i-1）的乘积。

普通打表 超内存+超时，，，

不妨将所有的输入数据都存进一个结构体中一个是no（表示输入时的顺序）一个是num（表示输入的数据n），再按照num的大小排序，之后依次找与num相等的数，并将其的值赋给out中

没想到还可以这样。。学习了

代码：

#include <cstdio>#include <cstring>#include <algorithm>#define LL __int64using namespace std;const LL M = 100005;const LL mod = 1000000007;struct node{LL no, num;}s[M];LL out[M];int cmp(node a, node b){return a.num < b.num;}int main(){LL n, cnt = 0;while(scanf("%I64d", &n) == 1){s[cnt].no = cnt;s[cnt].num = n;cnt++;}LL a, b, index = 0, i;sort(s, s+cnt, cmp);a = 1; b = 1;for(i = 1; index != cnt; i ++){a = (a*i)%mod;b = (b*a)%mod;while(index !=cnt &&s[index].num == i){out[s[index++].no] = b;}}for(i = 0; i < cnt; i ++){printf("%I64d\n", out[i]);}return 0;}