Time Limit: 10 Sec  Memory Limit: 64 MB

Submit: 1778  Solved: 827

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01分数规划+二分答案+spfa判负环

#include
#include
#include
#include
#include
#include
#define F(i,j,n) for(int i=j;i<=n;i++) #define D(i,j,n) for(int i=j;i>=n;i--)
#define ll long long
#define maxn 3005
#define maxm 10005
#define inf 1000000000
#define eps 1e-9
using namespace std;
struct edge{int next,to;double v,w;}e[maxm];
int n,m,cnt,head[maxn];
double dis[maxn];
bool flag,mark[maxn];
inline int read()
{
int x=0,f=1;char ch=getchar();
while (ch<'0'||ch>'9'){if (ch=='-') f=-1;ch=getchar();}
while (ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();} return x*f; } inline void add_edge(int x,int y) { e[++cnt].next=head[x]; e[cnt].to=y; head[x]=cnt; } inline void spfa(int x) { if (mark[x]){flag=true;return;} mark[x]=true; for(int i=head[x],y;i;i=e[i].next) if (dis[x]+e[i].v=eps)
{
mid=(l+r)/2;
F(i,1,m) e[i].v=e[i].w-mid;
if (judge()) r=mid;
else l=mid;
}
printf("%.8lf\n",l);
return 0;
}