ZOJ3033 Board Games

最短路径水题，SPFA处理吧，注意距离要用long long。

/******************************************************************************* # Author : Neo Fung # Email : [e-mail] # Last modified: 2012-04-18 19:48 # Filename: ZOJ3033 Board Games.cpp # Description :  ******************************************************************************/#ifdef _MSC_VER#define DEBUG#define _CRT_SECURE_NO_DEPRECATE#endif#include <fstream>#include <stdio.h>#include <iostream>#include <string.h>#include <string>#include <limits.h>#include <algorithm>#include <math.h>#include <numeric>#include <functional>#include <ctype.h>#include <vector>#include <stack>#define MAX 100010using namespace std;struct NODE{int v;long long w;};vector<NODE> edge[MAX];stack<int> stk;int n,ncase,m;int beg,end;int visit[MAX],in_stk[MAX];long long dist[MAX];int spfa(){memset(visit,0,sizeof(visit));memset(in_stk,0,sizeof(in_stk));for(int i=0;i<n;++i)dist[i]= ((long long)(1))<<61;while(!stk.empty())stk.pop();stk.push(beg);in_stk[beg]=1;dist[beg]=0;while(!stk.empty()){int u=stk.top();stk.pop();if(++visit[u]>n)return 0;// if(visit[end]>n)// return -1;in_stk[u]=0;for(size_t i=0;i<edge[u].size();++i){int v=edge[u][i].v;long long w=edge[u][i].w;if(dist[v]-dist[u]>w){dist[v]=dist[u]+w;if(!in_stk[v]){stk.push(v);in_stk[v]=1;}}}}return 1;}int main(void){#ifdef DEBUG  freopen("../stdin.txt","r",stdin);freopen("../stdout.txt","w",stdout); #endif  scanf("%d",&ncase);int u;while(ncase--){scanf("%d",&n);scanf("%d%d",&beg,&end);scanf("%d",&m);for(int i=0;i<n;++i)edge[i].clear();NODE nd_tmp;while(m--){scanf("%d%d%lld",&u,&nd_tmp.v,&nd_tmp.w);edge[u].push_back(nd_tmp);}int ans=spfa();if(dist[end]== ((long long)(1))<<61 || !ans)printf("infinity\n");elseprintf("%d\n",dist[end]);}return 0;}