THE MATRIX PROBLEM_差分约束_2018_3_18

#include<iostream>
#include<cmath>
#include<cstring>
using namespace std;
int n,m;
double l,u;
int num;
#define f(i,n) for(i=1;i<=n;i++)
const int N=1e4;

int vis
,head
;
double dis
;
struct AA{
int v,next;
double w;
}edge[N*N];

void add(int u,int v,double w){
edge[num].v=v;
edge[num].next=head[u];
edge[num].w=w;
head[u]=num++;
}

int spfa(int u){
vis[u]=1;
for(int h=head[u];h;h=edge[h].next){
int v=edge[h].v;
if(dis[v]>dis[u]+edge[h].w){
dis[v]=dis[u]+edge[h].w;
if(vis[v])return v;
int ret=spfa(v);
if(ret!=-1)return ret;
}
}
vis[u]=0;
return -1;
}

int solve(){
memset(vis,0,sizeof(vis));
memset(dis,0,sizeof(dis));
int i;
f(i,n+m){
int ret=spfa(i);
if(ret!=-1)return ret;
}
return -1;
}

int main(){
while(~scanf("%d%d%lf%lf",&n,&m,&l,&u)){
num=0;
memset(head,0,sizeof(head));
int i,j;
f(i,n)f(j,m){
double a;
scanf("%lf",&a);
add(j+n,i,log(u/a));
add(i,j+n,log(a/l));
}
if(solve()==-1)puts("YES");
else puts("NO");
}
}