22 lines
413 B
C
22 lines
413 B
C
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#include<stdio.h>
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unsigned long long sum[21],f[21];
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int main()
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{
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int i,t,n,m;
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f[0]=0;f[1]=0;f[2]=1;
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sum[0]=1;sum[1]=1;
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for(i=2;i<=20;i++)
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{
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sum[i]=sum[i-1]*i;
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if(i>=3)
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f[i]=(i-1)*(f[i-1]+f[i-2]);
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}
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scanf("%d",&t);
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while(t--)
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{
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scanf("%d%d",&n,&m);
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printf("%llu\n",sum[n]/sum[m]/sum[n-m]*f[m]);
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}
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return 0;
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}
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