[倍增 floyd] BZOJ 2165 大楼

#include<cstdio>
#include<cstdlib>
#include<algorithm>
#include<cstring>
using namespace std;
typedef long long ll;

inline char nc()
{
static char buf[100000],*p1=buf,*p2=buf;
if (p1==p2) { p2=(p1=buf)+fread(buf,1,100000,stdin); if (p1==p2) return EOF; }
return *p1++;
}

inline void read(ll &x)
{
char c=nc(),b=1;
for (;!(c>='0' && c<='9');c=nc()) if (c=='-') b=-1;
for (x=0;c>='0' && c<='9';x=x*10+c-'0',c=nc()); x*=b;
}

ll n,m,ans;
ll f[65][105][105];
ll t[105][105],g[105][105];

int main()
{
ll Q;
freopen("t.in","r",stdin);
freopen("t.out","w",stdout);
read(Q);
while (Q--)
{
read(n); read(m);
ans=0;
for (int p=0;p<=64;p++) for (int i=1;i<=n;i++) for (int j=1;j<=n;j++) f[p][i][j]=-1;
for (int i=1;i<=n;i++) for (int j=1;j<=n;j++) g[i][j]=-1;
for (int i=1;i<=n;i++) g[i][i]=0;
for (int i=1;i<=n;i++)
for (int j=1;j<=n;j++)
{
read(f[0][i][j]);
if (!f[0][i][j]) f[0][i][j]=-1;
}
int p;
try{
for (p=1;(1LL<<p)<=m;p++)
for (int k=1;k<=n;k++)
for (int i=1;i<=n;i++)
for (int j=1;j<=n;j++)
{
if (f[p-1][i][k]==-1 || f[p-1][k][j]==-1) continue;
f[p][i][j]=max(f[p][i][j],f[p-1][i][k]+f[p-1][k][j]);
if(i==1 && f[p][i][j]>=m)
throw(true);
}
} catch(bool) { }
while (p--)
{
for (int i=1;i<=n;i++) for (int j=1;j<=n;j++) t[i][j]=-1;
try{
for (int k=1;k<=n;k++)
for (int i=1;i<=n;i++)
for (int j=1;j<=n;j++)
{
if (g[i][k]==-1 || f[p][k][j]==-1) continue;
t[i][j]=max(t[i][j],g[i][k]+f[p][k][j]);
if (i==1 && t[i][j]>=m)
throw(true);
}
ans+=1LL<<p;
memcpy(g,t,sizeof(t));
} catch (bool) { }
}
ans++;
printf("%lld\n",ans);
}
return 0;
}