Review For Exam
[2019 福建省赛]
一个很简单的状态压缩DP，结果集体走偏
如何解决连续几日的限制问题？这种东西普通的DP很难写
#include <bits/stdc++.h>
#define ll long long
using namespace std;
const int maxn = 1010;
ll dp[maxn][1050];
ll val[maxn];
bool vis[1050];
const ll inf =0x3f3f3f3f3f3f3f3f;
int main() {
int n,k,a,b;
scanf("%d%d%d%d",&n,&k,&a,&b);
for(int i=1;i<=n;++i) scanf("%lld",&val[i]);
int mx=(1<<k)-1;
memset(dp,-0x3f3f3f3f,sizeof(dp));
for(int j=0,tmp;j<=mx;++j){
tmp=0;
for(int i=0;i<k;++i){
if((j>>i)&1){
tmp++;
}
}
if(tmp<=b&&tmp>=a) {
vis[j]=1;
dp[1][j]=0;
for(int i=0;i<k;++i){
if((j>>i)&1){
dp[1][j]+=val[k-i];
}else{
dp[1][j]-=val[k-i];
}
}
}
}
int tmp,tmpp,op;
for(int i=2;i<=n-k+1;++i){
for(int j=0;j<=mx;++j){
if(vis[j]){
tmp=j>>1;
tmpp=tmp+(1<<(k-1));
op=j%2;
if(op){
if(vis[tmp])
dp[i][j]=max(dp[i-1][tmp]+val[i+k-1],dp[i][j]);
if(vis[tmpp])
dp[i][j]=max(dp[i-1][tmpp]+val[i+k-1],dp[i][j]);
}else{
if(vis[tmp])
dp[i][j]=max(dp[i-1][tmp]-val[i+k-1],dp[i][j]);
if(vis[tmpp])
dp[i][j]=max(dp[i-1][tmpp]-val[i+k-1],dp[i][j]);
}
}
}
}
ll ans=-inf;
for(int j=0;j<=mx;++j){
ans=max(dp[n-k+1][j],ans);
}
printf("%lld\n",ans);
return 0;
}