Uvalive 6885 Flowery Trails shortest-circuit enumeration

Topic Connection:

http://acm.hust.edu.cn/vjudge/problem/visitOriginUrl.action?id=129723

Test instructions

Give you an n-point m-Graph edge

1 to n There are multiple shortest circuits, asking you what the sum of all the edges

Exercises

SPFA on the shortest path of single source for 1,n

Enumerates whether an edge is the shortest edge

i.e. Benquan +disa[i] + disb[i] = Shortest circuit length, is the answer

#include <bits/stdc++.h>using namespacestd;Const intN = 1e6+ -, M = 1e6+Ten, mod = 1e9+7, INF = 1e9+ +; typedefLong Longll;intHead[n],t,vis[n],dis[n],n,m,disa[n],disb[n];structedge{intTo,value,next;} e[n*2];voidAddintUintVintW) {e[t].next=head[u],e[t].to=v,e[t].value=w;head[u]=t++;}voidinit () {T=0; memset (Head,-1,sizeof(head));}voidSPFA (intu) { for(intI=1; i<=n;i++) Dis[i] = inf, vis[i] =0; vis[1] =1; Dis[u]=0; Queue<int>Q;    Q.push (U);  while(!Q.empty ()) {        intK =Q.front (); Q.pop (); VIS[K]=0;  for(inti=head[k];i!=-1; i=E[i].next) {            intto =e[i].to; if(Dis[k] + E[i].value <Dis[to]) {Dis[to]= Dis[k] +E[i].value; if(!Vis[to])                    {Q.push (to); Vis[to]=1; }            }        }    }}intMain () { while(~SCANF ("%d%d",&n,&m)) {init ();  for(intI=1; i<=m;i++) {            intA,b,c; scanf ("%d%d%d",&a,&b,&c); A++,b++;            Add (A,B,C);        Add (B,A,C); } SPFA (1);  for(intI=1; i<=n;i++) Disa[i] =Dis[i];        SPFA (n);  for(intI=1; i<=n;i++) Disb[i] =Dis[i]; intMX = dis[1]; ll ans=0;  for(intI=1; i<=n;i++) {             for(intj=head[i];j!=-1; j=E[j].next) {                intto =e[j].to; intValue =E[j].value; if(Disa[i] + disb[to] + value = = mx) ans+=value; }} printf ("%lld\n", 2ll*ans); }}

Uvalive 6885 Flowery Trails shortest-circuit enumeration