[POJ2047] Concert Hall Scheduling && 费用流

#include<cstdio>  
#include<algorithm>  
#include<cstring>  
#include<vector>  
#include<queue>
#include<deque>
#define SF scanf  
#define PF printf  
using namespace std;  
const int INF = 0x3f3f3f3f;  
const int MAXN = 2000;  
struct Node {  
    int u, v, c, f, cost;  
};
struct node {
    int s, t, w;
    bool operator < (const node &t) const {
        return s < t.s;
    }
}A[MAXN+10];
template <int maxn>  
struct MCMF {  
    int n, m, s, t;  
    vector <Node> Edge;  
    vector <int> G[maxn+10];  
    int inq[maxn+10], d[maxn+10], p[maxn+10], a[maxn+10];  
    void init(int n) {  
        this->n = n;  
        for(int i = 0; i < n; i++) G[i].clear();  
        Edge.clear();  
    }  
    void add(int u, int v, int c, int cost) {  
        Edge.push_back((Node) { u, v, c, 0, cost } );  
        Edge.push_back((Node) { v, u, 0, 0, -cost } );  
        m = Edge.size();  
        G[u].push_back(m-2); G[v].push_back(m-1);  
    }  
    bool SPFA(int s, int t, int &Flow, int &Cost)  
    {  
        for(int i = 0; i <= t; i++) d[i] = -INF;
        memset(inq, 0, sizeof(inq));  
        d[s] = 0; inq[s] = 1; p[s] = 0; a[s] = INF;  
        deque <int> q;  
        q.push_front(s);  
        while(!q.empty())  
        {  
            int u = q.front(); q.pop_front();  
            inq[u] = 0;  
            for(int i = 0; i < G[u].size(); i++)  
            {  
                int v = Edge[G[u][i]].v, c = Edge[G[u][i]].c, f = Edge[G[u][i]].f, cost = Edge[G[u][i]].cost;  
                if(c > f && d[v] < d[u] + cost) {  
                    d[v] = d[u] + cost;  
                    p[v] = G[u][i];  
                    a[v] = min(a[u], c - f);  
                    if(!inq[v]) {
                        inq[v] = true; 
                        if(d[v] > q.front()) q.push_front(v);
                        else q.push_back(v);
                    }  
                }  
            }  
        }  
        if(d[t] == -INF) return false;  
        Flow += a[t];  
        Cost += d[t] * a[t];  
        int u = t;  
        while(u != s) {  
            Edge[p[u]].f += a[t];  
            Edge[p[u]^1].f -= a[t];  
            u = Edge[p[u]].u;  
        }  
        return true;  
    }  
    int Mincost(int s, int t) {  
        int Flow = 0, Cost = 0;  
        for(int i = 0; i < 2; i++)
            SPFA(s, t, Flow, Cost);  
        return Cost;  
    }  
};  
MCMF <MAXN+10> sap;  
int main()
{
    int n;
    while(SF("%d", &n) && n)
    {
        for(int i = 1; i <= n; i++) SF("%d%d%d", &A[i].s, &A[i].t, &A[i].w);
        sort(A+1, A+1+n);
        int S = 0, T = 2 * n + 1;
        sap.init(T);
        for(int i = 1; i <= n; i++)
        {
            sap.add(S, i, 1, 0);
            sap.add(i, i+n, 1, A[i].w);
            sap.add(i+n, T, 1, 0);
        }
        for(int i = 1; i <= n; i++)
        {
            int j = i + 1;
            while(A[j].s <= A[i].t) j++;
            for( ; j <= n; j++) sap.add(i+n, j, 1, 0);
        }
        int ans = sap.Mincost(S, T);
        PF("%d\n", ans);
    }
}