蒟蒻用的BFS只拿90分，第十个测试点没过，求调！

#include <iostream>
#include <queue>
using namespace std;

const int N = 4e2 + 10;
int n,m,x,y,ans[N][N];
bool vis[N][N];

struct Bit
{
    int x,y,v;
};
queue <Bit> q;

void bfs()
{
    q.push({x,y,0});
    int _x = x,_y = y;
    while (!q.empty())
    {
        Bit tot = q.front();
        q.pop();
        int x = tot.x,y = tot.y,v = tot.v;
        if (vis[x][y] || x > n || x < 1 || y > m || y < 1) continue;
        vis[x][y] = 1;
        ans[x][y] = v;
        q.push({x + 2,y + 1,v + 1});
        q.push({x + 1,y + 2,v + 1});
        q.push({x - 2,y + 1,v + 1});
        q.push({x - 1,y + 2,v + 1});
        q.push({x + 2,y - 1,v + 1});
        q.push({x + 1,y - 2,v + 1});
        q.push({x - 1,y - 2,v + 1});
        q.push({x - 2,y - 1,v + 1});
    }
    for(int i = 1;i <= n;i ++)
        for(int j = 1;j <= m;j ++)
            if (ans[i][j] == 0 && i != _x && j != _y)
                ans[i][j] = -1;
}

int main()
{
    cin >> n >> m >> x >> y;
    bfs();
    for(int i = 1;i <= n;i ++)
    {
        for(int j = 1;j <= m;j ++)
        	printf("%d ",ans[i][j]);
        printf("\n");
	}
    return 0;
}