Usaco topic sharing--bessie Come Home

Bessie Come Home
Kolstad & Burch

It ' s dinner time, and the cows is out in their separate pastures. Farmer John rings The bell so they would start walking to the barn. Your job is-to-figure out which one cow gets to the barn first (the supplied test data would always have exactly one fastes T cow).

Between milkings, each cow was located in her own pasture, though some pastures has no cows in them. Each pasture are connected by a path to one or more pastures (potentially including itself). Sometimes, potentially self-same pastures is connected by more than one path. One or more of the pastures have a path to the barn. Thus, all cows has a path to the barn and they always know the shortest path. Of course, cows can go either direction on a path and they all walk at the same speed.

The pastures is labeled ' a '. ' Z ' and ' A '. ' Y '. One cow is in each pasture labeled with a capital letter. No Cow is in a pasture labeled with a lower case letter. The Barn ' s label is ' Z '; No cows is in the barn, though.

Program Name:comehomeinput FORMAT

Line 1:	Integer p (1 <= P <= 10000) the number of paths that interconnect the pastures (and the barn)
Line 2..p+1:	Space separated, letters and an integer:the names of the interconnected pastures/barn and the distance between them ( 1 <= Distance <= 1000)

SAMPLE INPUT (file comehome.in)

5 a D 6B d 3C e 9d z 8e z 3

OUTPUT FORMAT

A single line containing-items:the capital letter name of the pasture of the cow that arrives first back at the barn, The length of the path followed by that cow.

SAMPLE OUTPUT (file comehome.out)

B 11

This topic is a very classic short-circuit problem, to pay attention to is the treatment of a,a,z and so on. Build, then Spfa,dijikstra ... Yes, this problem has no card. Bare questions can be practiced hand.

#include <cstdio>#include<cstring>#include<iostream>#include<algorithm>#include<vector>#include<map>#include<deque>using namespacestd;intN;vector<int> f[10005],w[10005];intMex10005],o,oo;map<Char,int>u;Charname[10005],ansname;intzhong,ans=2000000000;intinf=2000000000;intdist[10005],inch[10005];voidSPFA (intz) {    inti,j; Deque<int>DP;  for(i=1; i<=oo;++i) {Dist[i]=inf; inch[i]=0; }    inch[z]=1;d ist[z]=0;    Dp.push_front (z);  while(!Dp.empty ()) {i=Dp.front ();        Dp.pop_front (); inch[i]=0;  for(j=0; J<f[i].size (); + +j) {intto=F[i][j]; if(dist[i]<inf&&dist[to]>dist[i]+W[i][j]) {Dist[to]=dist[i]+W[i][j]; if(!inch[to]) {                    inch[to]=1; if(!Dp.empty ()) {                        if(dist[to]<Dist[dp.front ()]) Dp.push_front (to); ElseDp.push_back (to); }                    ElseDp.push_back (to); }            }        }    }    if(dist[zhong]<ans) {ans=Dist[zhong]; Ansname=Name[z]; }}intMain () {Freopen ("comehome.in","R", stdin); Freopen ("Comehome.out","W", stdout); inti,j; scanf ("%d",&N); Chardu; scanf ("%c",&du); Charb; intC;  for(i=1; i<=n;++i) {scanf ("%c%c%d",&a,&b,&c); scanf ("%c",&du); if(u[a]==0) {oo++; U[a]=Oo; Name[oo]=A; }        if(u[b]==0) {oo++; U[B]=Oo; Name[oo]=b;        } f[u[a]].push_back (U[b]);        W[u[a]].push_back (c);        F[u[b]].push_back (U[a]);        W[u[b]].push_back (c); if(a=='Z') zhong=U[a]; if(a>='A'&&a<='Y') {o++; Ne[o]=U[a]; }        if(b=='Z') zhong=U[b]; if(b>='A'&&b<='Y') {o++; Ne[o]=U[b]; }    }     for(i=1; i<=o;++i) {SPFA (ne[i]); } printf ("%c%d\n", Ansname,ans); return 0;}

Usaco topic sharing--bessie Come Home