poj 1273 最大流入门
明天再拍一遍
1 #include <iostream> 2 #include <queue> 3 using namespace std; 4 const int N = 210; 5 const int INF = 0x7FFFFFFF; 6 int n,m,map[N][N],path[N],flow[N],start,end; 7 queue<int> q; 8 int bfs() 9 { 10 int i,t; 11 while(!q.empty()) q.pop(); 12 memset(path,-1,sizeof(path)); 13 path[start]=0,flow[start]=INF; 14 q.push(start); 15 while(!q.empty()) 16 { 17 t=q.front(); 18 q.pop(); 19 if(t==end) break; 20 for(i=1;i<=m;i++) 21 { 22 if(i!=start && path[i]==-1 && map[t][i]) 23 { 24 flow[i]=flow[t]<map[t][i]?flow[t]:map[t][i]; 25 q.push(i); 26 path[i]=t; 27 } 28 } 29 } 30 if(path[end]==-1) return -1; 31 return flow[m]; //一次遍历之后的流量增量 32 } 33 int Edmonds_Karp() 34 { 35 int max_flow=0,step,now,pre; 36 while((step=bfs())!=-1) 37 { //找不到增路径时退出 38 max_flow+=step; 39 now=end; 40 while(now!=start) 41 { 42 pre=path[now]; 43 map[pre][now]-=step; //更新正向边的实际容量 44 map[now][pre]+=step; //添加反向边 45 now=pre; 46 } 47 } 48 return max_flow; 49 } 50 int main() 51 { 52 int i,u,v,cost; 53 while(scanf("%d %d",&n,&m)!=EOF) 54 { 55 memset(map,0,sizeof(map)); 56 for(i=0;i<n;i++) 57 { 58 scanf("%d %d %d",&u,&v,&cost); 59 map[u][v]+=cost; //not just only one input 60 } 61 start=1,end=m; 62 printf("%d\n",Edmonds_Karp()); 63 } 64 return 0; 65 }
