POJ 1201 （差分约束）

1176 加权版 

……还是差分约束

Program P1201;var   n,i,j,minq,maxq:longint;   d:array[-1..60000] of longint;   w:array[1..60000,1..3] of longint;   flag:boolean;function min(a,b:longint):longint;begin   if a<b then exit(a) else exit(b);end;function max(a,b:longint):longint;begin   if a>b then exit(a) else exit(b);end;procedure relax(v,u,w:longint);begin   if (d[u]+w<d[v]) then   begin      d[v]:=d[u]+w;      flag:=false;   end;end;procedure bellman_ford;var   i,j,k:longint;begin   //d[w[i,2]] - d[w[i,1]-1]>=2 ->d[w[i,1]-1]-d[w[i,2]]<=-2   //d[i]-d[i-1]<=1   //d[i]-d[i-1]>=0 ->d[i-1]-d[i]<=0   d[minq-1]:=0;   while (true) do   begin      flag:=true;//    for i:=minq to maxq do relax(i,minq-1,0);      for i:=1 to n do relax(w[i,1]-1,w[i,2],-w[i,3]);      for i:=minq to maxq do relax(i,i-1,1);      for i:=maxq downto minq do relax(i-1,i,0);      if flag then break;   end;end;begin   while not seekeof do   begin      minq:=maxlongint;  maxq:=0;      fillchar(d,sizeof(d),0);      read(n);      for i:=1 to n do      begin         read(w[i,1],w[i,2],w[i,3]);         minq:=min(minq,w[i,1]);         maxq:=max(maxq,w[i,2]);      end;      bellman_ford;      writeln(d[maxq]-d[minq-1]);   end;end.