进入 dfs 之前标记

#include <bits/stdc++.h>
using namespace std;
int n, m, t;
int sx, sy, fx, fy;
bool g[10][10];
int ans;
bool vis[10][10];
int dx[] = {0, 0, 1, -1};
int dy[] = {1, -1, 0, 0};
void dfs(int x, int y)
{
    if (x == fx && y == fy)
    {
        ans++;
        return;
    }
    for (int i = 0; i <= 3; i++)
    {
        int xx = x + dx[i];
        int yy = y + dy[i];
        if (1 <= xx && xx <= n &&
            1 <= yy && yy <= m &&
            g[xx][yy] == false &&
            vis[xx][yy] == false)
        {
            vis[xx][yy] = true;
            dfs(xx, yy);
            vis[xx][yy] = false;
        }
    }
}
int main()
{
    cin >> n >> m >> t;
    cin >> sx >> sy >> fx >> fy;
    for (int i = 1; i <= t; i++)
    {
        int x, y;
        cin >> x >> y;
        g[x][y] = true;
    }
    ans = 0;
    vis[sx][sy] = true;
    dfs(sx, sy);
    vis[sx][sy] = false;
    cout << ans;
    return 0;
}

进入 dfs 之后标记

#include <bits/stdc++.h>
using namespace std;
int n, m, t;
int sx, sy, fx, fy;
bool g[10][10];
int ans;
bool vis[10][10];
int dx[] = {0, 0, 1, -1};
int dy[] = {1, -1, 0, 0};
void dfs(int x, int y)
{
    if (x == fx && y == fy)
    {
        ans++;
        return;
    }
    vis[x][y] = true;
    for (int i = 0; i <= 3; i++)
    {
        int xx = x + dx[i];
        int yy = y + dy[i];
        if (1 <= xx && xx <= n &&
            1 <= yy && yy <= m &&
            g[xx][yy] == false &&
            vis[xx][yy] == false)
        {
            dfs(xx, yy);
        }
    }
    vis[x][y] = false;
}
int main()
{
    cin >> n >> m >> t;
    cin >> sx >> sy >> fx >> fy;
    for (int i = 1; i <= t; i++)
    {
        int x, y;
        cin >> x >> y;
        g[x][y] = true;
    }
    ans = 0;
    dfs(sx, sy);
    cout << ans;
    return 0;
}