金中欢乐赛 A题

题目传送门

这道题就贪心.... 正的一坨和负的一坨间隔

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<queue>
#include<cmath>
#include<cstdlib>
#define LL long long
using namespace std;
const int M=500007;
LL read(){
    LL ans=0,f=1,c=getchar();
    while(c<'0'||c>'9'){if(c=='-') f=-1; c=getchar();}
    while(c>='0'&&c<='9'){ans=ans*10+(c-'0'); c=getchar();}
    return ans*f;
}
LL lx[M],rx[M],w[M];
LL n,k,tot;
LL cnt=1;
LL sum[M],ans;
bool f[M];
struct node{
    LL w,pos;
    bool operator<(const node &x) const{return w>x.w;}
};
priority_queue<node>q;
LL pd(LL x){return x>=0?x:-x;}
int main()
{
    //freopen("input.in","r",stdin);
    LL v;
    n=read(); k=read();
    for(int i=1;i<=n;i++){
        v=read();
        if(v*sum[cnt]>=0) sum[cnt]+=v;
        else sum[++cnt]=v;
    }
    if(sum[1]*sum[cnt]>=0) sum[1]=sum[cnt]+sum[1],cnt--;
    for(int i=1;i<=cnt;i++) 
        if(sum[i]>0) ans+=sum[i],tot++; 
    //printf("%lld\n",ans);
    if(tot<=k){printf("%lld\n",ans); return 0;}
    LL now=tot-k; //printf("[%lld]\n",ans);
    q.push((node){pd(sum[1]),1}); 
    lx[1]=cnt; rx[1]=2; w[1]=pd(sum[1]);
    q.push((node){pd(sum[cnt]),cnt});
    lx[cnt]=cnt-1; rx[cnt]=1; w[cnt]=pd(sum[cnt]);
    for(int i=2;i<cnt;i++)  
        q.push((node){pd(sum[i]),i}),lx[i]=i-1,rx[i]=i+1,w[i]=pd(sum[i]);//printf("%d\n",pd(sum[i])); 
    //printf("[%d]\n",now);
    while(now){
        node x=q.top(); q.pop();
        LL k=x.pos;
        if(f[k]) continue;
        //printf("%lld\n",w[k]);
        ans-=w[k]; now--;
        LL l=lx[k],r=rx[k];
        f[l]=1; f[r]=1;
        cnt++;
        sum[cnt]=sum[k]+sum[l]+sum[r];
        w[cnt]=pd(sum[cnt]);
        q.push((node){w[cnt],cnt});
        lx[cnt]=lx[l]; rx[cnt]=rx[r];
        rx[lx[l]]=cnt; lx[rx[r]]=cnt;  
    }
    //printf("%lld\n",cnt);
    printf("%lld\n",ans);
    return 0;
}