題目:POJ-1273最大流模板題
code1：鏈式前向星(1)
#include
#include
#include
#define MAXN 205
#define MAXM 410
#define INT_MAX 0x7fffffff
using namespace std;
int n,m;
struct node { int c,next,to; } edge[MAXM]; int cnt,head[MAXN];
void addedge(int from,int to,int c)//這裏存的還是一條有向邊
{ edge[cnt].to=to; edge[cnt].c=c; edge[cnt].next=head[from]; head[from]=cnt++; edge[cnt].to=from; edge[cnt].c=0; edge[cnt].next=head[to]; head[to]=cnt++;
}
intgap[MAXN],h[MAXN],curedges[MAXN],pre[MAXN];
int start,end;
int SAP_GAP()
{ start=1; end=n;
//gap; h：距離標號數組；curedges：當前弧數組；pre前驅數組
int cur_flow,flow_ans=0,u,tmp,neck,i;// 初始化最大0
memset (h,0,sizeof(h));
memset(gap,0,sizeof(gap));
memset(pre,-1,sizeof(pre));
for(i=1; i<=n; i++) curedges[i]=head[i];//初始化當前弧爲第一條鄰接邊
gap[0]=n; u=start;
while(h[start]<</span>n)
{ if(u==end)
{ cur_flow=INT_MAX;
for(i=start; i!=end; i=edge[curedges[i]].to)
{ if(cur_flow>edge[curedges[i]].c)
{ neck=i; cur_flow=edge[curedges[i]].c; }
} //增廣成功，尋找瓶頸邊
for(i=start; i!=end; i=edge[curedges[i]].to)
{ tmp=curedges[i];
edge[tmp].c-=cur_flow; edge[tmp^1].c=cur_flow;
}
flow_ans+=cur_flow; u=neck;
}
for(i=curedges[u]; i!=-1; i=edge[i].next)
(edge[i].c&&h[u]==h[edge[i].to]+1) break; //尋找可行弧 if
if(i!=-1) //找到可行弧
{ curedges[u]=i; pre[edge[i].to]=u; u=edge[i].to; }
else //未找到可行弧
{ gap[h[u]]--;
if(gap[h[u]]==0) break; //GAP優化
curedges[u]=head[u];
for(tmp=n,i=head[u]; i!=-1; i=edge[i].next)
if(edge[i].c) tmp=min(tmp,h[edge[i].to]);
h[u]=tmp+1;
++gap[h[u]];
if(u!=start) u=pre[u];
}
}
return flow_ans;
}
void init()
{int from,to,c; cnt=0;
memset (head,-1,sizeof(head));
for(int i=0; i<</span>m; i++)
{ scanf("%d%d%d",&from,&to,&c); addedge(from,to,c); }
}
int main()
{ //freopen("in.txt","r",stdin);
(~scanf("%d%d",&m,&n)) while
{ init();
printf("%d\n",SAP_GAP());
}
return 0;
}
code2：鏈式前向星(2)
#include
#include
#include
#defineinf 0x7fffffff
using namespace std;
const int N=205;
const int M=500;//邊是雙向存的（注意不是無向）要開正常的2倍大
struct Edge { int v,next,w; } edge[M]; int head[N],cnt,n,m,s=1;
int pre[N],cur[N],dis[N],gap[N];
void addedge(int u,int v,int w)//這裏存的還是一條有向邊
{edge [cnt].v=v; edge[cnt].w=w;
[cnt].next=head[u]; head[u]=cnt++; edge
[cnt].v=u; edge[cnt].w=0; edge
[cnt].next=head[v]; head[v]=cnt++; edge
}
int sap()
{int flow=0,aug=inf,u; bool flag;
(pre,-1,sizeof(pre)); memset(dis,0,sizeof(dis)); memset
(gap,0,sizeof(gap)); memset
(int i=1; i<=n; i++) for
[i]=head[i]; cur
[s]=n; //初始化時全部處於gap[s] gap
=pre[s]=s; u
(dis[s]<</span>n) while
{ =0; flag
(int &j=cur[u]; j!=-1; j=edge[j].next) for
{int v=edge[j].v;
(edge[j].w>0&&dis[u]==dis[v]+1) if
flag=1; {
(edge[j].w<</span>aug) aug=edge[j].w; if
[v]=u; u=v; pre
(u==n) //如果到達end if
{ +=aug; flow
(u!=s) while
{ =pre[u]; u
[cur[u]].w-=aug; edge
edge [cur[u]^1].w+=aug;//異或是找與其配對的邊
}
=inf; aug
}
; break
}
}
if(flag) //未找到可行邊
continue;
int mindis=n;
for(int j=head[u]; j!=-1; j=edge[j].next)
{ int v=edge[j].v;
if(edge[j].w>0&&dis[v]<</span>mindis)
{ mindis =dis[v]; cur[u]=j; }
}
if((--gap[dis[u]])==0) break;
dis[u]=mindis+1;
gap[dis[u]]++;
u=pre[u];
}
return flow;
}
void init()
{ int from,to,c;
cnt=0;
memset(head,-1,sizeof(head));
for(int i=0;i<</span>m;i++)
{ scanf("%d%d%d",&from,&to,&c); addedge(from,to,c); }
}
int main()
{while(~scanf("%d%d",&m,&n))
{
init();
printf ("%d\n",sap());
}
0; return
}
code3：鄰接矩陣
#include
#include
#include
#define M 205
using namespace std;
const int inf=~0U>>1;
int n,nb,nc,m;
int gap[M],flow[M][M],dist[M],cur[M]; int pre[M]; int source,end,s,t;
int sap()
{ s=source; t=end;
memset(cur,0,sizeof(cur)); memset(dist,0,sizeof(dist)); memset(gap,0,sizeof(gap));
int u=pre[s]=s,maxflow=0,aug=inf;
gap[0]=n;
while(dist[s]<</span>n)
{
loop:
for(int v=cur[u];v<=n;v++)
{ if(flow[u][v]&&dist[u]==dist[v]+1)
{
cur[u]=v; aug=min(aug,flow[u][v]);
pre[v]=u; u=v;
if(v==t)
{ maxflow+=aug;
for(u=pre[u];v!=s;v=u,u=pre[u])
flow[u][v]-=aug,flow[v][u]+=aug;
aug=inf;
}
goto loop;
}
}
int mind=n;
for(int v=1;v<=n;v++)
if(flow[u][v]&&(mind>dist[v]))
{ cur[u]=v; mind=dist[v]; }
if((--gap[dist[u]])==0) break;
gap[dist[u]=mind+1]++;
u=pre[u];
}
return maxflow;
}
void init()
{ int from,to,c;
memset(flow,0,sizeof(flow));//沒加這個 wa了4次
for(int i=0;i<</span>m;i++)
{ scanf("%d%d%d",&from,&to,&c); flow[from][to]+=c; }
source=1; end=n;
}
int main()
{ int x,y,c;
while(~scanf("%d%d",&m,&n))
{
init();
printf("%d\n",sap());
}
return 0;
}
