POJ 1273 Edmonds_Karp

模拟后项弧

#include <stdio.h>#include <string.h>#define N 202#define INF 0x3fffffff#define _cls(a) memset(a,0,sizeof(a))int f[N][N];//current flowint c[N][N];//capacityint mark[N];// 0 -1 1 搜索过bool vis[N];//标记过int prev[N];//前继int d[N];//当前增加的flowint qu[N];//BFS queueint Min (int a,int b){return a>b? b:a;}int max_flow(int n,int s,int t)//souce sink{int top,base,u,v,flow=0;_cls(f);do{_cls(d);_cls(mark);_cls(vis);qu[0]=s;vis[s]=1;d[s]=INF;for (base=0,top=1;base!=top && !vis[t];)//bfs 如果sink被标记就结束{for (u=qu[base],v=1;v<=n;v++){if (!vis[v])//对每个未被标记的点{vis[v]=1;if (c[u][v] && f[u][v]<c[u][v])//如果(u,v)存在 flow而且没有满{d[v]=Min(d[u],c[u][v]-f[u][v]);mark[v]=1;prev[v]=u;qu[top++]=v;}else if (f[v][u])//反向弧 沿弧的反方向抵消原来的flow{d[v]=Min(d[u],f[v][u]);mark[v]=-1;prev[v]=u;qu[top++]=v;}else vis[v]=0;//如果以上2项都不符合 不算visited}}base++;}if (!vis[t]) break;//没有增广路了flow+=d[t];//printf("++%d ",d[t]);for (u=t;u!=s;)//倒回去 增加增广路上的flow{v=u;//printf("%c ",v+'A'-1);u=prev[v];f[u][v]+=d[t]*mark[v];}//printf("/n");}while(d[t]>0);return flow;}int main (){//freopen("1273.txt","r",stdin);int n,m,a,b,w;while(scanf("%d%d",&m,&n)!=EOF){_cls(c);while(m--){scanf("%d%d%d",&a,&b,&w);c[a][b]+=w;//有相同flow多次}printf("%d/n",max_flow(n,1,n));}}

有后项弧

#include <stdio.h>#include <string.h>#define N 202#define INF 0x3fffffff#define _cls(a) memset(a,0,sizeof(a))int c[N][N];//当前 capacitybool vis[N];//标记过int prev[N];//前继int d[N];//当前增加的flowint qu[N];//BFS queueint Min (int a,int b){return a>b? b:a;}int max_flow(int n,int s,int t)//souce sink{int top,base,u,v,flow=0;do{_cls(d);_cls(vis);qu[0]=s;vis[s]=1;d[s]=INF;for (base=0,top=1;base!=top && !vis[t];)//bfs 如果sink被标记就结束{for (u=qu[base],v=1;v<=n;v++){if (!vis[v] && c[u][v])//对每个未被标记的点{vis[v]=1;d[v]=Min(d[u],c[u][v]);prev[v]=u;qu[top++]=v;}}base++;}if (!vis[t]) break;//没有增广路了flow+=d[t];//printf("++%d ",d[t]);for (u=t;u!=s;)//倒回去 增加增广路上的flow{v=u;//printf("%c ",v+'A'-1);u=prev[v];c[u][v]-=d[t];c[v][u]+=d[t];//后项弧}//printf("/n");}while(d[t]>0);return flow;}int main (){//freopen("1273.txt","r",stdin);int n,m,a,b,w;while(scanf("%d%d",&m,&n)!=EOF){_cls(c);while(m--){scanf("%d%d%d",&a,&b,&w);c[a][b]+=w;//有相同flow多次}printf("%d/n",max_flow(n,1,n));}}

 

 

 12 7
1 2 5
1 3 7
1 4 4
2 3 1
2 6 3
3 4 2
3 5 5
3 6 4
4 5 4

 

 等于14