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-9; const int N=50+5,maxn=20+5,inf=999999; 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 0;//节点访问过 vis[u]=1; for(i=1;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 0; } int main() { ios::sync_with_stdio(false); cin.tie(0); // cout<<setiosflags(ios::fixed)<<setprecision(2); int T,cnt=0; cin>>T; while(T--){ cin>>n>>m; memset(c,0,sizeof(c)); memset(vis,0,sizeof(vis)); for(int i=1;i<=m;i++) { int u,v,w; cin>>u>>v>>w; c[u][v]+=w; } t=n;//t是汇点 int maxflow=0,flow; while(flow=dfs(1,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,0,sizeof(vis)); } cout<<"Case "<<++cnt<<": "<<maxflow<<endl; } return 0; }
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-9; const int N=50+5,maxn=20+5,inf=999999; 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,0,sizeof vis); memset(pre,0,sizeof pre); vis[1]=1; queue<int>q; q.push(1); while(!q.empty()){ int x=q.front(); q.pop(); if(x==t)return 1; for(int i=1;i<=n;i++) { if(!vis[i]&&c[x][i]) { q.push(i); pre[i]=x;//记录前驱 vis[i]=1; } } } return 0; } int max_flow() { int ans=0; while(1){ if(!bfs())return ans;//找不到增广路了 int minn=999999; for(int i=t;i!=1;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!=1;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(0); // cout<<setiosflags(ios::fixed)<<setprecision(2); int k,cnt=0; cin>>k; while(k--){ cin>>n>>m; memset(c,0,sizeof(c)); for(int i=1;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 0; }
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-9; const int N=100+10,maxn=16,inf=9999999; int n,s,t;//超级源超级汇 int v[N][N],dis[N]; bool bfs() { memset(dis,-1,sizeof dis); queue<int>q; q.push(s); dis[s]=0; while(!q.empty()){ int x=q.front(); q.pop(); for(int i=1;i<=n;i++) { if(v[x][i]&&dis[i]==-1) { dis[i]=dis[x]+1; q.push(i); } } } if(dis[t]==-1)return 0; return 1; } int dfs(int x,int mx) { int a; if(x==t)return mx; for(int i=1;i<=n;i++) { if(v[x][i]>0&&dis[i]==dis[x]+1&&(a=dfs(i,min(mx,v[x][i])))) { v[x][i]-=a; v[i][x]+=a; return a; } } return 0; } int main() { ios::sync_with_stdio(false); cin.tie(0); int k,m,cnt=0; cin>>k; while(k--){ cin>>n>>m; memset(v,0,sizeof v); while(m--){ int a,b,c; cin>>a>>b>>c; v[a][b]+=c; } int ans=0,flow; s=1,t=n; while(bfs()){ while(flow=dfs(s,inf))ans+=flow; } cout<<"Case "<<++cnt<<": "<<ans<<endl; } return 0; }