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https://github.com/Kiritow/OJ-Problems-Source.git
synced 2024-03-22 13:11:29 +08:00
26 lines
442 B
C++
26 lines
442 B
C++
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#include<stdio.h>
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int con(int n,int m)
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{
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__int64 a=1,b=1,i;
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for(i=1;i<=m;i++,n--)
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{
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b*=i;a*=n;
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}
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return a/b;
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}
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int main()
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{
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int i,n;
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__int64 t,a[13];
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a[0]=1;a[1]=0;a[2]=1;a[3]=2;
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for(i=4;i<=12;i++)
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a[i]=(i-1)*(a[i-1]+a[i-2]);
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while(scanf("%d",&n)!=EOF&&n!=0)
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{
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t=0;
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for(i=0;i<=n/2;i++)
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t+=a[i]*con(n,i);
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printf("%I64d\n",t);
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}
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}
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