实现功能:同前
程序还是一如既往的优美,虽然比起邻接矩阵的稍稍长了那么些,不过没关系这是必然,但更重要的一个必然是——速度将是一个质的飞跃^_^(这里面的point指针稍作了些创新——anti指针,这个指向当前弧的反向弧,便于路径增广时的操作,相比非递归里面非要用一个op函数来挨个找已经强多了!!!)
1 type
2 point=^node;
3 node=record
4 g,w:longint;
5 anti,next:point;
6 end;
7 var
8 i,j,k,l,m,n,ans,s,t:longint;
9 a:array[0..10000] of point;
10 d,dv:array[0..10000] of longint;
11 function min(x,y:longint):longint;inline;
12 begin
13 if x<y then min:=x else min:=y;
14 end;
15 procedure add(x,y,z:longint);inline;
16 var p:point;
17 begin
18 new(p);p^.g:=y;p^.w:=z;p^.next:=a[x];a[x]:=p;
19 new(p);p^.g:=x;p^.w:=0;p^.next:=a[y];a[y]:=p;
20 a[y]^.anti:=a[x];a[x]^.anti:=a[y];
21 end;
22 function dfs(x,flow:longint):longint;inline;
23 var i,j,k,l:longint;p:point;
24 begin
25 if x=t then exit(flow);
26 dfs:=0;p:=a[x];
27 while p<>nil do
28 begin
29 if (p^.w>0) and (d[x]=(d[p^.g]+1)) then
30 begin
31 k:=dfs(p^.g,min(flow-dfs,p^.w));
32 dec(p^.w,k);
33 inc(p^.anti^.w,k);
34 inc(dfs,k);
35 if dfs=flow then exit;
36 end;
37 p:=p^.next;
38 end;
39 if d[s]=n then exit;
40 dec(dv[d[x]]);
41 if dv[d[x]]=0 then d[s]:=n;
42 inc(d[x]);inc(dv[d[x]]);
43 end;
44 begin
45 readln(n,m,s,t);
46 for i:=1 to n do a[i]:=nil;
47 for i:=1 to m do
48 begin
49 readln(j,k,l);
50 add(j,k,l);
51 end;
52 fillchar(d,sizeof(d),0);
53 fillchar(dv,sizeof(dv),0);
54 dv[0]:=n;ans:=0;
55 while d[s]<n do inc(ans,dfs(s,maxlongint));
56 writeln(ans);
57 end.