bzoj 1221: [HNOI2001] 软件开发

思路：把每天拆乘两个点Xi, Yi 两堆点

建边过程：

1、从S向每个Xi连一条容量为a[ i ]，费用为0的有向边。

2、从每个Yi向T连一条容量为a[ i ]，费用为0的有向边。

3、从S向每个Yi连一条容量为inf，费用为c1的有向边。

4、从每个Xi向Xi + 1(i+1<=N)连一条容量为inf，费用为0的有向边。

5、从每个Xi向Yi + p + 1(i + p + 1 <= N)连一条容量为inf，费用为f的有向边。

6、从每个Xi向Yi + q + 1(i + q + 1<=N)连一条容量为inf，费用为s的有向边。

注意：能少建边就少见边，我刚开始因为建了接近n^2的边就T啦。。

费用流拉的别人的板子， 有空自己手敲一个。。。

#include<bits/stdc++.h>
#define LL long long
#define fi first
#define se second
#define mk make_pair
#define pii pair<int,int>
#define piii pair<int,pair<int,int>>

using namespace std;

const int N = 2000 + 7;
const int M = 5e5 + 7;
const int inf = 0x3f3f3f3f;
const LL INF = 0x3f3f3f3f3f3f3f3f;
const int mod = 1e9 + 7;

int n, p, q, c1, c2, c3, a[N];

struct Edge
{
    int from, to, cap, flow, cost, next;
};
Edge edge[M];
int head[N], edgenum;
int pre[N];
int dist[N];
bool vis[N];
int source, sink;
void init()
{
    edgenum = 0;
    memset(head, -1, sizeof(head));
}
void addEdge(int u, int v, int w, int c)
{
    Edge E1 = {u, v, w, 0, c, head[u]};
    edge[edgenum] = E1;
    head[u] = edgenum++;
    Edge E2 = {v, u, 0, 0, -c, head[v]};
    edge[edgenum] = E2;
    head[v] = edgenum++;
}
bool SPFA(int s, int t)
{
    queue<int> Q;
    memset(dist, INF, sizeof(dist));
    memset(vis, false, sizeof(vis));
    memset(pre, -1, sizeof(pre));
    dist[s] = 0;
    vis[s] = true;
    Q.push(s);
    while(!Q.empty())
    {
        int u = Q.front();
        Q.pop();
        vis[u] = false;
        for(int i = head[u]; i != -1; i = edge[i].next)
        {
            Edge E = edge[i];
            if(dist[E.to] > dist[u] + E.cost && E.cap > E.flow)
            {
                dist[E.to] = dist[u] + E.cost;
                pre[E.to] = i;
                if(!vis[E.to])
                {
                    vis[E.to] = true;
                    Q.push(E.to);
                }
            }
        }
    }
    return pre[t] != -1;
}
void MCMF(int s, int t, LL &cost, int &flow)
{
    flow = 0;
    cost = 0;
    while(SPFA(s, t))
    {
        int Min = INF;
        for(int i = pre[t]; i != -1; i = pre[edge[i^1].to])
        {
            Edge E = edge[i];
            Min = min(Min, E.cap - E.flow);
        }
        //增广
        for(int i = pre[t]; i != -1; i = pre[edge[i^1].to])
        {
            edge[i].flow += Min;
            edge[i^1].flow -= Min;
            cost += edge[i].cost * Min;
        }
        flow += Min;
    }
}
int main() {
    init();
    scanf("%d%d%d%d%d%d", &n, &p, &q, &c1, &c2, &c3);
    source = 0, sink = 2 * n + 1;
    for(int i = 1; i <= n; i++) {
        scanf("%d", &a[i]);
        addEdge(source, i + n, a[i], c1);
        addEdge(i + n, sink, a[i], 0);
        addEdge(source, i, a[i], 0);
    }

    for(int i = 1; i <= n; i++) {
        for(int j = i + p + 1; j < i + q + 1 && j <= n; j++)
            addEdge(i, j + n, a[i], c2);
        for(int j = i + q + 1; j <= n; j++)
            addEdge(i, j + n, a[i], c3);
    }

    LL cost;
    int flow;
    MCMF(source, sink, cost, flow);
    printf("%lld
", cost);
    return 0;
}