53 lines
1.2 KiB
C++
53 lines
1.2 KiB
C++
#include<cstdio>
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#include<algorithm>
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using namespace std;
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template<typename T> inline void read(T& t)
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{
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t=0; bool f=false; char ch;
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while(ch=getchar(),!((ch>='0'&&ch<='9')||ch=='-'));
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if(ch=='-') f=true,ch=getchar();
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t=ch-'0';
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while(ch=getchar(),ch>='0'&&ch<='9') t=t*10+ch-'0';
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if(f) t=-t;
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}
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template<typename T,typename... Args> inline void read(T& t,Args&... args) { read(t); read(args...); }
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const int maxn=1000010;
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struct Node { int kind,p; };
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inline bool operator<(const Node &a,const Node &b) { return a.p<b.p; }
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Node a[maxn];
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int hsh[70],ans=1e9+7,Ti,n,l=0,k,sum=0;
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int que[maxn],head,tail;
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int main()
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{
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#ifdef local
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freopen("pro.in","r",stdin);
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#endif
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read(n,k);
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for(int i=1;i<=k;i++)
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{
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read(Ti);
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while(Ti-->0)
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{
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int p; read(p);
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a[++l].p=p; a[l].kind=i;
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}
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}
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sort(a+1,a+n+1);
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for(int i=1;i<=n;i++)
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{
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que[tail++]=i;
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hsh[a[i].kind]++;
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if(hsh[a[i].kind]==1) sum++;
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while(sum==k)
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{
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Node &e=a[que[tail-1]],&s=a[que[head]];
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if(ans>e.p-s.p) ans=e.p-s.p;
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head++;
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hsh[s.kind]--;
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if(hsh[s.kind]==0) sum--;
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}
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}
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printf("%d\n",ans);
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return 0;
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}
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