"Differential constraint system/dfs version SPFA" bzoj3436-Small K Farm

"The main topic"

A total of n farms, the following three kinds of description: Farm a more than farm b at least planted a C units of the crop, farm a than farm B to grow more than a C units of the crop, farm A and farm B planted as many crops. Ask if there is a possibility.

Ideas

Farm A has at least more than farm B plants planted with C units: A>=b+c→b<=a-c, A to B with a-C edge.

Farm A has grown more than farm B with a C-unit crop: A<=b+c, which is connected by B to a side of C.

Farm A has as many crops as farm B: a=b→b<=a<=b, with a 0 edge to each other.

SPFA to judge negative ring, to use the DFS version. DFS version of the direct reference to the Rausen seniors ... It's really fast to fly (; ′⌒ ')

1#include <bits/stdc++.h>2 using namespacestd;3 Const intmaxn=10000+ -;4 structEdge5 {6     intTo,len;7 };8 intn,m;9Vector<edge>E[MAXN];Ten intVis[maxn],dis[maxn],flag; One  A voidAddedge (intUintVintW) - { - E[u].push_back (Edge) {v,w}); the } -  - voidInit () - { +scanf"%d%d",&n,&m); -      for(intI=1; i<=m;i++) +     { A         intop,a,b,c; atscanf"%d",&op); -         if(op==1)//A-b>=c -         { -scanf"%d%d%d",&a,&b,&c); -Addedge (a,b,-c); -         } in         if(op==2) -         { toscanf"%d%d%d",&a,&b,&c); + Addedge (b,a,c); -         } the         if(op==3) *         { $scanf"%d%d",&a,&b);Panax NotoginsengAddedge (A, B,0); Addedge (B,a,0); -         } the     } + } A  the voidSPFA (intfr) + { -     if(VIS[FR]) $     { $flag=1; -         return; -     } thevis[fr]=1; -      for(intI=0; I<e[fr].size (); i++)Wuyi     { the         intto=e[fr][i].to,len=E[fr][i].len; -         if(dis[fr]+len<Dis[to]) Wu         { -dis[to]=dis[fr]+Len; About SPFA (to); $             if(flag)return; -         } -     } -vis[fr]=0; A } +  the voidSolve () - { $memset (Vis,0,sizeof(Vis)); the      for(intI=1; i<=n;i++) the     { the SPFA (i); the         if(flag) Break; -     } inPuts (flag?)"No":"Yes"); the } the  About intMain () the { the init (); the solve (); +     return 0; -}

"Differential constraint system/dfs version SPFA" bzoj3436-Small K Farm