过河卒

转自http://blog.youkuaiyun.com/cm_yali/article/details/50607787

#include<stdio.h>  
#include<stdlib.h>  
int a[30][30];  
long long f[30][30];  
void draw(int x,int y){  
    int i,j,k;  
    if(x<0 || x>20 || y<0 || y>20)  
        return;  
    else a[x][y]=1;      
}  
int main(){  
    int i,j,k,m,n,x,y;  
    scanf("%d%d%d%d",&m,&n,&x,&y);  
    draw(x,y);  
    draw(x+1,y+2);  
    draw(x+2,y+1);  
    draw(x+2,y-1);  
    draw(x+1,y-2);  
    draw(x-1,y-2);  
    draw(x-2,y-1);  
    draw(x-2,y+1);  
    draw(x-1,y+2);  
    for(i=1;i<=n;i++)  
      if(a[0][i]!=1)f[0][i]=1;  
        else break;  
    for(i=1;i<=m;i++)  
      if(a[i][0]!=1)f[i][0]=1;  
        else break;  
    for(i=1;i<=m;i++)  
      for(j=1;j<=n;j++)  
        if(!a[i][j])  
           f[i][j]=f[i-1][j]+f[i][j-1];  
    printf("%lld\n",f[m][n]);  
    return 0;      
}