题意: 给定一个数NNN,问有多少组a,b,ca,b,ca,b,c满足a+bc=Na+\dfrac bc=Na+cb=N,且a,b,ca,b,ca,b,c三个数不重不漏地涵盖1−91-91−9这999个数字,输出总组数
解题思路:
#include
using namespace std;vector num{1,2,3,4,5,6,7,8,9};int check(int l,int r)
{int sum=0;for(int i=l;i<=r;i++)sum=sum*10+num[i];return sum;
}int main()
{int n;cin>>n;int res=0;do{for(int i=0;i<9;i++)for(int j=i+1;j<9;j++){int a=check(0,i);int b=check(i+1,j);int c=check(j+1,8);if(a==0 || b==0 || c==0) continue;if(a*c+b==c*n) res++;}}while(next_permutation(num.begin(),num.end()));cout<