题意: 给出一个长度为n的序列 n<=1000 ,存在一个置换。 按照置换规则重新变成1-n 需要多少次？
对于所有可能的对应关系，有多少种可能的排数？
例如 原序列是1 2 3
给出置换规则 1->2 2->3 3->1
1 2 3
2 3 1
3 1 2
1 2 3
我们发现，置换了3次就恢复原序列了。
分析:
感谢sunsetcolors大佬的思路, 我们可以把这个置换看做一个图, 那么我们可以发现，置换必定出先循环节
上面这个1 2 3 例子，置换的循环节就是3.也就是说，我们要恢复，需要3次 = 循环节长度。
再举个例子，例如 1->2->3->1 4->5 6->6 可以发现，循环节长度分别是 3 2 1 。 可以手算答案=6次
可以得出 ans=lcm(3,2,1)=6
那么就是把问题变成，分解n，有多少种不同的lcm。 为了不考虑损耗，采用质因子来分解配凑。
必定 pri^k1 + pri^k2 + .... pri^kn <= n
下面就是一个完全背包的经典问题
代码:
#pragma GCC optimize(1)
#pragma GCC optimize(2)
#pragma GCC optimize(3)
#pragma GCC optimize("Ofast")
#pragma GCC optimize("inline")
#pragma GCC optimize("-fgcse")
#pragma GCC optimize("-fgcse-lm")
#pragma GCC optimize("-fipa-sra")
#pragma GCC optimize("-ftree-pre")
#pragma GCC optimize("-ftree-vrp")
#pragma GCC optimize("-fpeephole2")
#pragma GCC optimize("-ffast-math")
#pragma GCC optimize("-fsched-spec")
#pragma GCC optimize("unroll-loops")
#pragma GCC optimize("-falign-jumps")
#pragma GCC optimize("-falign-loops")
#pragma GCC optimize("-falign-labels")
#pragma GCC optimize("-fdevirtualize")
#pragma GCC optimize("-fcaller-saves")
#pragma GCC optimize("-fcrossjumping")
#pragma GCC optimize("-fthread-jumps")
#pragma GCC optimize("-funroll-loops")
#pragma GCC optimize("-fwhole-program")
#pragma GCC optimize("-freorder-blocks")
#pragma GCC optimize("-fschedule-insns")
#pragma GCC optimize("inline-functions")
#pragma GCC optimize("-ftree-tail-merge")
#pragma GCC optimize("-fschedule-insns2")
#pragma GCC optimize("-fstrict-aliasing")
#pragma GCC optimize("-fstrict-overflow")
#pragma GCC optimize("-falign-functions")
#pragma GCC optimize("-fcse-skip-blocks")
#pragma GCC optimize("-fcse-follow-jumps")
#pragma GCC optimize("-fsched-interblock")
#pragma GCC optimize("-fpartial-inlining")
#pragma GCC optimize("no-stack-protector")
#pragma GCC optimize("-freorder-functions")
#pragma GCC optimize("-findirect-inlining")
#pragma GCC optimize("-frerun-cse-after-loop")
#pragma GCC optimize("inline-small-functions")
#pragma GCC optimize("-finline-small-functions")
#pragma GCC optimize("-ftree-switch-conversion")
#pragma GCC optimize("-foptimize-sibling-calls")
#pragma GCC optimize("-fexpensive-optimizations")
#pragma GCC optimize("-funsafe-loop-optimizations")
#pragma GCC optimize("inline-functions-called-once")
#pragma GCC optimize("-fdelete-null-pointer-checks")
#pragma G++ optimize(1)
#pragma G++ optimize(2)
#pragma G++ optimize(3)
#pragma G++ optimize("Ofast")
#pragma G++ optimize("inline")
#pragma G++ optimize("-fgcse")
#pragma G++ optimize("-fgcse-lm")
#pragma G++ optimize("-fipa-sra")
#pragma G++ optimize("-ftree-pre")
#pragma G++ optimize("-ftree-vrp")
#pragma G++ optimize("-fpeephole2")
#pragma G++ optimize("-ffast-math")
#pragma G++ optimize("-fsched-spec")
#pragma G++ optimize("unroll-loops")
#pragma G++ optimize("-falign-jumps")
#pragma G++ optimize("-falign-loops")
#pragma G++ optimize("-falign-labels")
#pragma G++ optimize("-fdevirtualize")
#pragma G++ optimize("-fcaller-saves")
#pragma G++ optimize("-fcrossjumping")
#pragma G++ optimize("-fthread-jumps")
#pragma G++ optimize("-funroll-loops")
#pragma G++ optimize("-fwhole-program")
#pragma G++ optimize("-freorder-blocks")
#pragma G++ optimize("-fschedule-insns")
#pragma G++ optimize("inline-functions")
#pragma G++ optimize("-ftree-tail-merge")
#pragma G++ optimize("-fschedule-insns2")
#pragma G++ optimize("-fstrict-aliasing")
#pragma G++ optimize("-fstrict-overflow")
#pragma G++ optimize("-falign-functions")
#pragma G++ optimize("-fcse-skip-blocks")
#pragma G++ optimize("-fcse-follow-jumps")
#pragma G++ optimize("-fsched-interblock")
#pragma G++ optimize("-fpartial-inlining")
#pragma G++ optimize("no-stack-protector")
#pragma G++ optimize("-freorder-functions")
#pragma G++ optimize("-findirect-inlining")
#pragma G++ optimize("-frerun-cse-after-loop")
#pragma G++ optimize("inline-small-functions")
#pragma G++ optimize("-finline-small-functions")
#pragma G++ optimize("-ftree-switch-conversion")
#pragma G++ optimize("-foptimize-sibling-calls")
#pragma G++ optimize("-fexpensive-optimizations")
#pragma G++ optimize("-funsafe-loop-optimizations")
#pragma G++ optimize("inline-functions-called-once")
#pragma G++ optimize("-fdelete-null-pointer-checks")
#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <string>
#include <vector>
#include <map>
#include <queue>
#include <deque>
#include <set>
#include <stack>
#include <cctype>
#include <cmath>
#include <cassert>
#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define INF 0x3f3f3f3f
#define PI 3.14159265358979323846
#define esp 1e-8
#define int long long
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const ll mod=1000000007;
ll powmod(ll a,ll b) {ll res=1;a%=mod; assert(b>=0); for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}
ll gcd(ll a,ll b) { return b?gcd(b,a%b):a;}
int dir[4][2]={{0,-1},{-1,0},{0,1},{1,0}};
int dir2[8][2]={{-1,-1},{-1,1},{1,-1},{1,1},{0,-1},{-1,0},{0,1},{1,0}};
template <typename _T>
inline void read(_T &f)
{
f = 0; _T fu = 1; char c = getchar();
while (c < '0' || c > '9') { if (c == '-') { fu = -1; } c = getchar(); }
while (c >= '0' && c <= '9') { f = (f << 3) + (f << 1) + (c & 15); c = getchar(); }
f *= fu;
}
template <typename T>
void print(T x)
{
if (x < 0) putchar('-'), x = -x;
if (x < 10) putchar(x + 48);
else print(x / 10), putchar(x % 10 + 48);
}
template <typename T>
void print(T x, char t)
{
print(x); putchar(t);
}
const int N=1005;
int n;
int a[N];
int tot;
int pri[N];
int dp[N];
int prime()
{//打素数表
a[0]=1;
a[1]=1;
for(int i=2;i<=n;i++)
{
if(a[i]==0)
{
pri[tot++]=i;
for(int j=i*i;j<=n;j+=i)
{
a[j]=1;
}
}
}
return tot;
}
signed main()
{
scanf("%lld",&n);
int m=prime();
dp[0]=1;
//完全背包
for(int i=0;i<m;i++)
{
for(int j=n;j>=pri[i];j--)
{
int x=pri[i];
while(x<=j)
{
dp[j]+=dp[j-x];
x*=pri[i];
}
}
}
int ans=0;
for(int i=0;i<=n;i++)
{
ans+=dp[i];
}
printf("%lld\n",ans);
return 0;
}
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