poj 1201 差分约束+SPFA

/*
s[b+1]-s[a]>=c
s[i+1]-s[i]>=0
s[i]-s[i+1]>=-1
*/
#include
#include
#include
#include
#include
using namespace std;
#define maxn 50005
struct node
{
    int v,w,next;
}edge[maxn<<2];

int id,end,st;
int a,b,c,n;
int head[maxn];
bool in[maxn];
int d[maxn];
void init()
{
    memset(head,-1,sizeof(head));
    end=id=0;
    st=0x3f3f3f3f;
}
void addedge(int a,int b,int c)
{
    edge[id].v=b;
    edge[id].w=c;
    edge[id].next=head[a];
    head[a]=id++;
}
void SPFA()
{
    queue Q;
    memset(in,0,sizeof(in));
    memset(d,-0x3f,sizeof(int)*(end+5));
    Q.push(0);
    in[0]=1;
    d[0]=0;
    int tmp;
    while(!Q.empty())
    {
        tmp=Q.front();Q.pop();
        in[tmp]=0;
        for(int i=head[tmp];i!=-1;i=edge[i].next)
        {
            if(d[edge[i].v]