#include<iostream>
#include<map>
using namespace std;
int n,a[30],k;
long long s,ans;
map<int,long long>f;
map<pair<long long,int>,bool>mp;
map<long long,bool>vis;
int mid;
void dfs_left(int t,long long sum,int cnt)
{
if(t>mid)
{
// int m=mp[{sum,cnt}];
// printf("%d %d %d\n",sum,cnt,mp[{sum,cnt}]);
mp[{sum,cnt}]++;
// if(m==mp[{sum,cnt}])printf("?");
// printf("%d %d %d\n\n\n\n",sum,cnt,mp[{sum,cnt}]);
vis[sum]=true;
return;
}
dfs_left(t+1,sum,cnt);
if(sum+a[t]<=s)dfs_left(t+1,sum+a[t],cnt);
if(a[t]<=20&&cnt<k&&sum+f[a[t]]<=s)dfs_left(t+1,sum+f[a[t]],cnt+1);
}
long long _count(long long sum,int cnt)
{
long long x=0;
for(int i=0;i<=cnt;i++)x+=mp[{sum,i}];
return x;
}
void dfs_right(int t,long long sum,int cnt)
{
if(t>n)
{
if(vis.find({s-sum})!=vis.end())ans+=_count(s-sum,k-cnt);
return;
}
dfs_right(t+1,sum,cnt);
if(sum+a[t]<=s)dfs_right(t+1,sum+a[t],cnt);
if(a[t]<=20&&cnt<k&&sum+f[a[t]]<=s)dfs_right(t+1,sum+f[a[t]],cnt+1);
}
int main()
{
f[1]=1;
for(int i=2;i<=20;i++)f[i]=f[i-1]*i;
scanf("%d%d%lld",&n,&k,&s);
mid=(n>>1);
for(int i=1;i<=n;i++)scanf("%d",&a[i]);
dfs_left(1,0,0);
dfs_right(mid+1,0,0);
// for(auto i:mp)printf("sum:%lld cnt:%d %d\n",i.first.first,i.first.second,i.second);
printf("\n");
printf("%lld",ans);
return 0;
}
这是一道暴搜,加注释为调试代码,删掉运行,打问号的意思是mp[{sum,cnt}]++这条代码神奇的没运行到(也可能是别的原因),就是说mp[{sum,cnt}]的值与执行完mp[{sum,cnt}]++后的值相同,求调。