poj 2983Is the Information Reliable?

差分约束用SPFA判断是否存在负数环  p的时候就是就是dis[B]- dis[A]>=w,dis[B]-dis[A]<=w,V就是dis[B]>=dis[A]+1

题目虽然没说A，B是1-n但是按照这样做过了。。。- -！！如果要的话，就hash一下呗

code：

#include<iostream>
#include<cstdio>
#include<cstring>
#include<vector>
#include<algorithm>
#include<queue>
using namespace std;
const int MAXB = 100011;
const int MAXN = 1010;
bool visit[MAXN];
int c[MAXN];
int dis[MAXN];
int n,m;
const int INF = 999999;
struct node{
int v,w;
node(int vv = 0,int ww = 0):v(vv),w(ww){}
};
vector<node> edge[MAXB];
int mins,maxs;
bool spfa(){
memset(visit,false,sizeof(visit));
memset(c,0,sizeof(c));
for(int i = 1;i<MAXN;i++)dis[i] = INF;
visit[0] = 1;
queue<int > qe;
qe.push(0);
c[0]++;
while(!qe.empty()){
int cur = qe.front();
qe.pop();
visit[cur] = 0;
for(int i = 0;i<edge[cur].size();i++){
if(dis[edge[cur][i].v]>edge[cur][i].w+dis[cur]){
dis[edge[cur][i].v] = dis[cur]+edge[cur][i].w;
c[edge[cur][i].v]++;
if(c[edge[cur][i].v]>n)return false;
if(!visit[edge[cur][i].v]){
qe.push(edge[cur][i].v);
visit[edge[cur][i].v] = 1;
}
}
}
}
return true;
}
int main()
{

while(scanf("%d%d",&n,&m)!=EOF){
for(int i = 0;i<MAXN;i++)edge[i].clear();
int v,u,w;
 mins = MAXN+1;
 maxs = -1;
char p[20];
for(int i = 0;i<m;i++){
scanf("%s",p);
if(p[0]=='P'){
scanf("%d%d%d",&u,&v,&w);
edge[u].push_back(node(v,w));
edge[v].push_back(node(u,-w));
}else {
scanf("%d%d",&u,&v);
edge[v].push_back(node(u,-1));
}
}
for(int i = 1;i<MAXN;i++)edge[0].push_back(node(i,0));
if(spfa())printf("Reliable\n");
else printf("Unreliable\n");
}
return 0;
}