網絡流最大流模板-劉汝佳-dinic鄰接表建圖

例題：

Flow Problem

 

Network flow is a well-known difficult problem for ACMers. Given a graph, your task is to find out the maximum flow for the weighted directed graph.

Input

The first line of input contains an integer T, denoting the number of test cases. 
For each test case, the first line contains two integers N and M, denoting the number of vertexes and edges in the graph. (2 <= N <= 15, 0 <= M <= 1000) 
Next M lines, each line contains three integers X, Y and C, there is an edge from X to Y and the capacity of it is C. (1 <= X, Y <= N, 1 <= C <= 1000)

Output

For each test cases, you should output the maximum flow from source 1 to sink N.

Sample Input

2
3 2
1 2 1
2 3 1
3 3
1 2 1
2 3 1
1 3 1

Sample Output

Case 1: 1
Case 2: 2

題意：就是給你每邊和權值求1-n源點到匯點的最大流，板子題

 

#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define inf 0x3f3f3f3f
const int maxn = 16;
struct Edge{
	int from, to, cap, flow;
	Edge(){
	}
	Edge(int from, int to, int cap, int flow):from(from), to(to), cap(cap), flow(flow){}	
};
struct Dinic{
	int n, m, s, t;
	vector<Edge>edges;
	vector<int>G[maxn];
	int d[maxn];
	int cur[maxn];
	int vis[maxn];
	void init(int n, int s, int t)
	{
		this->n = n;this->s = s;this->t = t;
		edges.clear();
		for(int i = 0;i <= n;++i) G[i].clear();
	}
	
	void add_edge(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); 
	}
	
	bool bfs(){
		memset(vis, 0, sizeof(vis));
		queue<int>Q;
		Q.push(s);
		d[s] = 0;
		vis[s] = true;
		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] = true;
					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()
	{
		int flow = 0;
		while(bfs())
		{
			memset(cur, 0, sizeof(cur));
			flow += dfs(s,inf);
		}
		return flow;
	}
}gao;//劉汝佳網絡流dinic板子
int main()
{
	int t;
	scanf("%d", &t);int cnt = 1;
	while(t--)
	{
		int n, m;
		scanf("%d%d", &n, &m);
		gao.init(n, 1, n);//初始化數組
		while(m--)
		{
			int u, v, w;
			scanf("%d%d%d", &u, &v, &w);
			gao.add_edge(u, v, w);//把每邊加入
		}
		printf("Case %d: %d\n",cnt++,gao.maxflow());//輸出最大流
	}
	return 0;
}