hdu3549(网络流)买一送一poj1273
这道题跟poj1273是一模一样的，只略微改变了几个地方，就ok了,更正下，上面的算法不叫Ford_Fulkerson ,而是EK
1 #include <cstdio> 2 #include <cstring> 3 #define Max 0x7f7f7f7f 4 int n,m; 5 int path[100][100]; 6 int visited[100]; 7 int que[10000]; 8 int pre[100]; 9 int flow[100]; 10 int min(int a ,int b) 11 { 12 return a>b?b:a; 13 } 14 int BFS()//查找有没有增广路 15 { 16 memset(visited,0,sizeof(visited)); 17 memset(pre,-1,sizeof(pre)); 18 memset(flow,Max,sizeof(flow)); 19 int head=0; 20 int tail=1; 21 que[head]=1; 22 visited[1]=1; 23 while(head<tail) 24 { 25 int tmp=que[head]; 26 if(tmp==n) break; 27 for(int i=2;i<=n;i++) 28 { 29 if(visited[i]==0 && path[tmp][i]!=0) 30 { 31 visited[i]=1; 32 pre[i]=tmp; 33 que[tail]=i; 34 flow[i]=min(flow[tmp],path[tmp][i]); 35 tail++; 36 37 } 38 } 39 head++; 40 } 41 if(visited[n]==0) 42 return -1; 43 else return flow[n];//有增广路 44 } 45 46 int Ford_Fulkerson() 47 { 48 int nowflow,maxflow=0; 49 while((nowflow=BFS())!=-1)//更新残余网络 50 { 51 maxflow+=nowflow; 52 int tmp=n; 53 while(tmp!=1) 54 { 55 int before=pre[tmp]; 56 path[before][tmp]-=nowflow; 57 path[tmp][before]+=nowflow; 58 tmp=before; 59 } 60 } 61 return maxflow; 62 } 63 64 int main() 65 { 66 int start,end,value; 67 int Case; 68 int k=1; 69 scanf("%d",&Case); 70 while(Case--) 71 { 72 scanf("%d%d",&n,&m); 73 memset(path,0,sizeof(path)); 74 for(int i=1;i<=m;i++) 75 { 76 scanf("%d%d%d",&start,&end,&value); 77 path[start][end]+=value; 78 } 79 printf("Case %d: %d\n",k++,Ford_Fulkerson()); 80 } 81 82 return 0; 83 }
