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How Many Points of Intersection?

2024-07-12 03:24:58   256人阅读

uva10790:http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=1731

题意：两条水平线，分别有n,m个点，点之间两两连线，求有多少个交点。

题解：手动模拟一下，然后用不完全归纳法，就可以得到公式ans=(n-1)*n/2*(m-1)*m/2;

 1 #include<iostream> 2 #include<cstdio> 3 #include<algorithm> 4 #include<cstring> 5 using namespace std; 6 long long m, n; 7 int main(){ 8     int tt=1; 9      while(~scanf("%lld%lld",&n,&m)){10         if(n==0&&m==0)break;11        printf("Case %d: %lld\n",tt++,(n-1)*n/2*(m-1)*(m)/2);12      }13 }
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