pku 2983 Is the Information Reliable?(差分约束系统)

#include <iostream>
using namespace std;
struct Edge
{
int x,y,dist;
}edges[200005];
int edge_num,N,M;
int dist_array[1005];
void AddEdge(int x,int y,int dist)
{
edges[edge_num].x=x;
edges[edge_num].y=y;
edges[edge_num].dist=dist;
edge_num++;
}
bool Bellman_Ford()
{
bool change;
for(int i=0;i<N;i++)
{
change=false;
for(int j=0;j<edge_num;j++)
{
if(dist_array[edges[j].x]+edges[j].dist<dist_array[edges[j].y])
{
dist_array[edges[j].y]=dist_array[edges[j].x]+edges[j].dist;
change=true;
}
}
}
return !change;
}
int main()
{
while(scanf("%d%d",&N,&M)!=EOF)
{
memset(dist_array,0,sizeof(dist_array));
edge_num=0;
int x,y,dist;
char flag;
for(int i=0;i<M;i++)
{
scanf("/n%c%d%d",&flag,&x,&y);
if(flag=='P')
{
scanf("%d",&dist);
AddEdge(x,y,-dist);
AddEdge(y,x,dist);
}
else
{
AddEdge(x,y,-1);
}
}
if(Bellman_Ford())
printf("Reliable/n");
else printf("Unreliable/n");
}
return 0;
}