hdu3549网络流之最大流

Ford-Fulkerson方法：dfs实现

dfs  140ms

#include<map>
#include<set>
#include<cmath>
#include<queue>
#include<stack>
#include<vector>
#include<cstdio>
#include<cassert>
#include<iomanip>
#include<cstdlib>
#include<cstring>
#include<iostream>
#include<algorithm>
#define pi acos(-1)
#define ll long long
#define mod 10007
#define ls l,m,rt<<1
#define rs m+1,r,rt<<1|1
#pragma comment(linker, "/STACK:1024000000,1024000000")

using namespace std;

const double g=10.0,eps=1e-;
const int N=+,maxn=+,inf=;

int t,n,m;
int vis[maxn];//判断是否访问过
int c[maxn][maxn];//邻接矩阵存图
int dfs(int u,int low)//深搜找增广路
{
    int i,flow;
    if(u==t)return low;//到达汇点
    if(vis[u])return ;//节点访问过
    vis[u]=;
    for(i=;i<=n;i++)
        if(c[u][i]&&(flow=dfs(i,low<c[u][i]?low:c[u][i])))
        {
            c[u][i]-=flow;
            c[i][u]+=flow;
            return flow;
        }
    return ;
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie();
 //   cout<<setiosflags(ios::fixed)<<setprecision(2);
    int T,cnt=;
    cin>>T;
    while(T--){
        cin>>n>>m;
        memset(c,,sizeof(c));
        memset(vis,,sizeof(vis));
        for(int i=;i<=m;i++)
        {
            int u,v,w;
            cin>>u>>v>>w;
            c[u][v]+=w;
        }
        t=n;//t是汇点
        int maxflow=,flow;
        while(flow=dfs(,inf))//当增广路还存在时
        {
           /* for(int i=1;i<=n;i++)
            {
                for(int j=1;j<=n;j++)
                    cout<<c[i][j]<<" ";
                cout<<endl;
            }*/
            maxflow+=flow;
            memset(vis,,sizeof(vis));
        }
        cout<<"Case "<<++cnt<<": "<<maxflow<<endl;
    }
    return ;
}

Edmonds_Karp算法：bfs实现

bfs 156ms

#include<map>
#include<set>
#include<cmath>
#include<queue>
#include<stack>
#include<vector>
#include<cstdio>
#include<cassert>
#include<iomanip>
#include<cstdlib>
#include<cstring>
#include<iostream>
#include<algorithm>
#define pi acos(-1)
#define ll long long
#define mod 10007
#define ls l,m,rt<<1
#define rs m+1,r,rt<<1|1
#pragma comment(linker, "/STACK:1024000000,1024000000")

using namespace std;

const double g=10.0,eps=1e-;
const int N=+,maxn=+,inf=;

int t,n,m,pre[N];
bool vis[maxn];//判断是否访问过
int c[maxn][maxn];//邻接矩阵存图
bool bfs()//判断是否存在增广路，并求出
{
    memset(vis,,sizeof vis);
    memset(pre,,sizeof pre);
    vis[]=;
    queue<int>q;
    q.push();
    while(!q.empty()){
        int x=q.front();
        q.pop();
        if(x==t)return ;
        for(int i=;i<=n;i++)
        {
            if(!vis[i]&&c[x][i])
            {
                q.push(i);
                pre[i]=x;//记录前驱
                vis[i]=;
            }
        }
    }
    return ;
}
int max_flow()
{
    int ans=;
    while(){
        if(!bfs())return ans;//找不到增广路了
        int minn=;
        for(int i=t;i!=;i=pre[i])
            minn=min(minn,c[pre[i]][i]);//找出增广路中最小的节点
        for(int i=t;i!=;i=pre[i])
        {
            c[pre[i]][i]-=minn;//更新残余网络
            c[i][pre[i]]+=minn;
        }
        ans+=minn;
    }
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie();
 //   cout<<setiosflags(ios::fixed)<<setprecision(2);
    int k,cnt=;
    cin>>k;
    while(k--){
        cin>>n>>m;
        memset(c,,sizeof(c));
        for(int i=;i<=m;i++)
        {
            int u,v,w;
            cin>>u>>v>>w;
            c[u][v]+=w;
        }
        t=n;//t是汇点
        cout<<"Case "<<++cnt<<": "<<max_flow()<<endl;
    }
    return ;
}

dinic算法：dfs+bfs实现

171ms（我可能用的是假的dinic，居然这么慢，可能数据比较弱）

#include<map>
#include<set>
#include<cmath>
#include<queue>
#include<stack>
#include<vector>
#include<cstdio>
#include<cassert>
#include<iomanip>
#include<cstdlib>
#include<cstring>
#include<iostream>
#include<algorithm>
#define pi acos(-1)
#define ll long long
#define mod 1000000007
#define ls l,m,rt<<1
#define rs m+1,r,rt<<1|1
#pragma comment(linker, "/STACK:1024000000,1024000000")

using namespace std;

const double g=10.0,eps=1e-;
const int N=+,maxn=,inf=;

int n,s,t;//超级源超级汇
int v[N][N],dis[N];
bool bfs()
{
    memset(dis,-,sizeof dis);
    queue<int>q;
    q.push(s);
    dis[s]=;
    while(!q.empty()){
        int x=q.front();
        q.pop();
        for(int i=;i<=n;i++)
        {
            if(v[x][i]&&dis[i]==-)
            {
                dis[i]=dis[x]+;
                q.push(i);
            }
        }
    }
    if(dis[t]==-)return ;
    return ;
}
int dfs(int x,int mx)
{
    int a;
    if(x==t)return mx;
    for(int i=;i<=n;i++)
    {
        if(v[x][i]>&&dis[i]==dis[x]+&&(a=dfs(i,min(mx,v[x][i]))))
        {
            v[x][i]-=a;
            v[i][x]+=a;
            return a;
        }
    }
    return ;
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie();
    int k,m,cnt=;
    cin>>k;
    while(k--){
        cin>>n>>m;
        memset(v,,sizeof v);
        while(m--){
            int a,b,c;
            cin>>a>>b>>c;
            v[a][b]+=c;
        }
        int ans=,flow;
        s=,t=n;
        while(bfs()){
            while(flow=dfs(s,inf))ans+=flow;
        }
        cout<<"Case "<<++cnt<<": "<<ans<<endl;
    }
    return ;
}