文章测试

#include <bits/stdc++.h>using namespace std;const int R = 8;const int C = 10;const int BR = 0; const int BC = 0; const int ER = 7;const int EC = 9;int dr[4] = {0, 1, 0, -1};i...

错位排列：D(n)=(n-1)*[D(n-2)+D(n-1)]。特殊的,D(0)=0,D(2)=1a-b=a ∩ !B