POJ 1459 Power Network

题意：题意炒鸡坑……有n个电站，有np个发电站，只发电，还有nc个用电站，只用电，剩下的都是中转站，然后有m条电缆，先给出每条电缆能输送的最大电量，再给出每个发电站的最大发电量，最后是每个用电站的最大用电量，求所有用电站最多用点的和。

 

解法：最大流。题目很裸……只是题意太罗嗦了……建图的时候因为是多源点多汇点，所以设一个超级源一个超级汇，超级源到每个源的边权即为源的最大发电量，超级汇同理。直接在大白上掏了个dinic的模板敲……各种敲错……初始化的范围还没写对各种wa……orz

 

代码：

#include<stdio.h>
#include<iostream>
#include<algorithm>
#include<string>
#include<string.h>
#include<math.h>
#include<limits.h>
#include<time.h>
#include<stdlib.h>
#include<map>
#include<queue>
#include<set>
#include<stack>
#include<vector>
#define LL long long
using namespace std;
const int maxn = 310;
const int inf = 0x3f3f3f3f;
int n, m, s, t;
vector <int> G[maxn];
bool vis[maxn];
int d[maxn];
struct Edge
{
    int from, to, cap, flow;
};
vector <Edge> edges;
void init()
{
    for(int i=0; i <= n + 10; i++) G[i].clear();
    edges.clear();
}
void addEdge(int from, int to, int cap)
{
    edges.push_back((Edge){from, to, cap, 0});
    edges.push_back((Edge){to, from, 0, 0});
    m = edges.size();
    G[from].push_back(m - 2);
    G[to].push_back(m - 1);
}
int cur[maxn];
bool bfs()
{
    memset(vis, 0, sizeof(vis));
    queue <int> q;
    q.push(s);
    d[s] = 0;
    vis[s] = 1;
    while(!q.empty())
    {
        int x = q.front(); q.pop();
        for(int i = 0; i < G[x].size(); i++)
        {
            Edge& e = edges[G[x][i]];
            if(!vis[e.to] && e.cap > e.flow)
            {
                vis[e.to] = 1;
                d[e.to] = d[x] + 1;
                q.push(e.to);
            }
        }
    }
    return vis[t];
}
int dfs(int x, int a)
{
    if(x == t || a == 0) return a;
    int flow = 0, f;
    for(int& i = cur[x]; i < G[x].size(); i++)
    {
        Edge& e = edges[G[x][i]];
        if(d[x] + 1 == d[e.to] && (f = dfs(e.to, min(a, e.cap - e.flow))) > 0)
        {
            e.flow += f;
            edges[G[x][i] ^ 1].flow -= f;
            flow += f;
            a -= f;
            if(a == 0) break;
        }
    }
    return flow;
}
int maxFlow()
{
    s = n + 1, t = n + 2;
    int flow = 0;
    while(bfs())
    {
        memset(cur, 0, sizeof cur);
        flow += dfs(s, inf);
    }
    return flow;
}
int main()
{
    int np, nc, k;
    while(~scanf("%d%d%d%d", &n, &np, &nc, &k))
    {
        init();
        while(k--)
        {
            int a, b, c;
            scanf(" (%d,%d)%d", &a, &b, &c);
            addEdge(a + 1, b + 1, c);
        }
        while(np--)
        {
            int a, b;
            scanf(" (%d)%d", &a, &b);
            addEdge(n + 1, a + 1, b);
        }
        while(nc--)
        {
            int a, b;
            scanf(" (%d)%d", &a, &b);
            addEdge(a + 1, n + 2, b);
        }
        printf("%d\n", maxFlow());
    }
    return 0;
}