BZOJ 2288: 【POJ Challenge】生日礼物 贪心 + 堆 + 链表

好像是模拟费用流

Code:

#include <bits/stdc++.h>
#define setIO(s) freopen(s".in","r",stdin)
#define P pair<int,int>
#define ll long long
#define maxn 100007
using namespace std;
int arr[maxn],l[maxn],r[maxn],mark[maxn];
priority_queue<P, vector<P>, greater<P> >q;
void del(int x) {
    l[r[x]]=l[x], r[l[x]]=r[x];
    mark[x]=1;
}
int main() {
    // setIO("input");
    int n,m,tmp=0,cnt=0;
    scanf("%d%d",&n,&m);
    for(int i=1;i<=n;++i) {
        int x;
        scanf("%d",&x);
        if(!x) continue;
        if(1ll*arr[tmp]*x>0) arr[tmp]+=x;
        else arr[++tmp]=x;
    }
    n=tmp;
    int sum=0;
    for(int i=1;i<=n;++i) {
        l[i]=i-1,r[i]=i+1;
        if(arr[i] > 0) ++cnt, sum+=arr[i];
        q.push(make_pair(abs(arr[i]), i));
    }
    while(cnt > m) {
        while(mark[q.top().second]) q.pop();
        int x=q.top().second;      q.pop();
        if((l[x]&&r[x]!=n+1) || arr[x] > 0) {
            sum-=abs(arr[x]);
            arr[x]+=arr[l[x]] + arr[r[x]];
            del(l[x]), del(r[x]);
            --cnt;
            q.push(make_pair(abs(arr[x]), x));
        }
        else del(x);
    }
    printf("%d\n",sum);
    return 0;
}