44 lines
862 B
C++
44 lines
862 B
C++
#include<cstdio>
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#include<cstring>
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using namespace std;
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int tree[1010][1010];
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int sum[1010][1010];
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int main()
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{ int i,j,k,n,m,x,y,ans,l,r,p,l2,r2,res;
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while(~scanf("%d%d",&n,&m))
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{ memset(tree,0,sizeof(tree));
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for(i=1;i<=m;i++)
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{ scanf("%d%d",&x,&y);
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tree[x][y]=1;
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}
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for(i=1;i<=n;i++)
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for(j=1;j<=n;j++)
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sum[i][j]=sum[i][j-1]+tree[i][j];
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ans=0;
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l2=1;r2=n;
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while(l2<r2)
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{ i=(l2+r2+1)/2;
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res=0;ans=0;
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for(j=1;j<=n-i+1;j++)
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{ l=j;r=j+i-1;p=0;
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for(k=1;k<=n;k++)
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{ if(sum[k][r]-sum[k][l-1]>0)
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p=0;
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else
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{ p++;
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if(p>=i)
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{ ans=i;
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break;
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}
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}
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}
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}
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if(ans>0)
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l2=i;
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else
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r2=i-1;
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}
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printf("%d\n",l2);
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}
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}
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