[贪心 堆 链表] BZOJ 3502 PA2012 Tanie linie

#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<algorithm>
using namespace std;
typedef long long ll;

inline char nc()
{
static char buf[100000],*p1=buf,*p2=buf;
if (p1==p2) { p2=(p1=buf)+fread(buf,1,100000,stdin); if (p1==p2) return EOF; }
return *p1++;
}

inline void read(ll &x)
{
char c=nc(),b=1;
for (;!(c>='0' && c<='9');c=nc()) if (c=='-') b=-1;
for (x=0;c>='0' && c<='9';x=x*10+c-'0',c=nc()); x*=b;
}

const ll N=1000005;

ll n,m,tmp,cnt;
ll _a
,v
;
ll pre
,next
;
ll ans,tot;

ll H[2*N],maxn;
ll back[2*N];

inline ll val(ll i) { return abs(v[H[i]]); }
inline ll F(ll i) { return (i<<1)==maxn?(i<<1):(val(i<<1)<val(i<<1|1)?(i<<1):(i<<1|1)); }
inline ll Swp(ll x,ll y) { swap(H[x],H[y]); swap(back[H[x]],back[H[y]]); }
inline void Down(ll x)
{
if (x>maxn) return;
for (ll i=x,tmp;(i<<1)<=maxn && val(tmp=F(i))<val(i);)
Swp(i,tmp),i=tmp;
}
inline void Up(ll x)
{
if (x>maxn) return;
for (ll i=x;i!=1 && val(i)<val(i>>1);)
Swp(i,i>>1),i>>=1;
}
inline void Del(ll x)
{
Swp(x,maxn);
maxn--;
Down(x);
Up(x);
}
inline void Ins(ll x)
{
H[++maxn]=x;
back[x]=maxn;
Up(maxn);
}

inline void Solve()
{
ll k,a,b;
for (ll i=1;i<=cnt;i++)
Ins(i);
while (tot>m)
{
k=H[1];
if (pre[k]==-1)
{
if (v[k]>0)
ans-=abs(v[k]),Del(1),tot--;
else
Del(1);
pre[next[k]]=pre[k];
}
else if (next[k]==-1)
{
if (v[k]>0)
ans-=abs(v[k]),Del(1),tot--;
else
Del(1);
next[pre[k]]=next[k];
}
else
{
ans-=abs(v[k]);
a=next[k]; b=pre[k];
pre[k]=pre[b]; if (pre[b]!=-1) next[pre[b]]=k;
next[k]=next[a]; if (next[a]!=-1) pre[next[a]]=k;
v[k]+=v[a]+v[b]; v[a]=v[b]=0;
Down(1);
Del(back[a]);
Del(back[b]);
tot--;
}
}
}

int main()
{
read(n); read(m);
for (ll i=1;i<=n;i++)
{
read(_a[++tmp]);
if (!_a[tmp]) tmp--;
}
v[++cnt]=_a[1];
for (ll i=2;i<=tmp;i++)
if ((_a[i]>0 && _a[i-1]>0) || (_a[i]<0 && _a[i-1]<0))
v[cnt]+=_a[i];
else
v[++cnt]=_a[i];
for (ll i=1;i<=cnt;i++)
if (v[i]>0)
ans+=v[i],tot++;
for (ll i=1;i<=cnt;i++)
pre[i]=i-1,next[i]=i+1;
pre[1]=next[cnt]=-1;
Solve();
printf("%lld\n",ans);
return 0;
}