http://www.lydsy.com/JudgeOnline/problem.php?id=3209 (题目链接)
题意
${sum(i)}$表示${i}$的二进制表示中${1}$的个数。求${\prod^n sum(i)}$
Solution
${f_{i,s}}$表示dp到第${i}$位，已经有${s}$个${1}$时的乘积。然后一路dfs就可以了。
细节
LL，返回值要与1取个max
代码
// bzoj3598
#include<algorithm>
#include<iostream>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<cmath>
#include<ctime>
#define LL long long
#define inf (1ll<<30)
#define MOD 10000007
#define Pi acos(-1.0)
#define free(a) freopen(a".in","r",stdin),freopen(a".out","w",stdout);
using namespace std;LL f[60][60],m;
int n,t[60];LL dfs(int pos,LL s,int lim) {if (!pos) return s;if (!lim && f[pos][s]!=-1) return f[pos][s];int end=lim ? t[pos] : 1;LL res=1;for (int i=0;i<=end;i++)(res*=max(1ll,dfs(pos-1,s+i,lim && i==end)))%=MOD;if (!lim) f[pos][s]=res;return res;
}
int main() {memset(f,-1,sizeof(f));scanf("%lld",&m);for (n=0;m;m>>=1) t[++n]=m&1;printf("%lld",dfs(n,0,1));return 0;
}
