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;  
}