题解

#include<bits/stdc++.h>
using namespace std;
long long a[25][25];
bool c[25][25];
int dx[9] = {0,-2,-1,1,2,2,1,-1,-2};
int dy[9] = {0,1,2,2,1,-1,-2,-2,-1};
int main(){
    int n,m,x,y;
    cin >> n >> m >> x >> y;
    x += 1,y += 1;
    for(int i = 0;i <= 8;i++){
    	int ax = x + dx[i];
    	int ay = y + dy[i];
    	if(ax > 0 && ax <= n + 1 && ay > 0 && ay <= m + 1) c[ax][ay] = true;
    }
    a[1][1] = 1;
	for(int i = 1;i <= n + 1;i++){
		for(int j = 1;j <= m + 1;j++){
			if(a[i][j]){
                continue;
            } 
			if(c[i][j]){
               continue; 
            } 
			a[i][j] = a[i - 1][j] + a[i][j - 1];
		}
	}
	cout << a[n + 1][m + 1];
    return 0;
}