暴力万岁

#include<bits/stdc++.h> long long B[21][21]; int main(void) { int i,j,n,m,a,b; scanf("%d%d%d%d",&n,&m,&a,&b); for(i=0;i<=n;i++) for(j=0;j<=m;j++) B[i][j]=1; if(a-2>=0&&b-1>=0) B[a-2][b-1]=0;
if(a-2>=0&&b+1<=m) B[a-2][b+1]=0; if(a-1>=0&&b-2>=0) B[a-1][b-2]=0; if(a-1>=0&&b+2<=m) B[a-1][b+2]=0; if(a+1<=m&&b-2>=0) B[a+1][b-2]=0; if(a+2<=n&&b-1>=0) B[a+2][b-1]=0; if(a+1<=n&&b+2<=m) B[a+1][b+2]=0; if(a+1<=n&&b+1<=m) B[a+2][b+1]=0; B[a][b]=0; for(i=0;i<=n;i++){ for(j=0;j<=m;j++){ if(B[i][j]){ if(i==0&&j==0) continue; else if(i==0) B[i][j]=B[i][j-1]; else if(j==0) B[i][j]=B[i-1][j]; else B[i][j]=B[i-1][j]+B[i][j-1]; } } } printf("%lld",B[n][m]);
return 0; }