更尴尬的是结尾cnt / 2，得了30分，实在检查了很久，思路也是对的，希望能指出错误，谢谢

#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <stack>
#define IOS ios::syns_with_stdio(false),cin.tie(NULL),cout.tie(NULL);
using namespace std;

const int maxn = 1e4 + 5;
int n, m, t;
int p[maxn][maxn];
bool vis[maxn][maxn];
int cnt = 0;

void dfs(int x, int y) {
	vis[x][y] = true;
	if (p[x][y] == 3) {
		++cnt;
		return ;
	}
	for (int i = -1; i <= 1; ++i) {
		for (int j = -1; j <= 1; ++j) {
			if (x + i > 0 && y + j > 0 && x + i <= n && y + j <= m && p[x + i][y + j] != 2 && vis[x + i][y + j] == false) {
				dfs(x + i, y + j);
				vis[x + i][y + j] = false;
			}
		}
	}
}

int main() {
	int x1, y1;
	int x, y;
	scanf("%d %d %d", &n, &m, &t);
	scanf("%d %d", &x1, &y1);
	scanf("%d %d", &x, &y);
	p[x][y] = 3;//终点
	for (int i = 0; i < t; ++i) {
		scanf("%d %d", &x, &y);
		p[x][y] = 2;
	}
	dfs(x1, y1);
	printf("%d", cnt);
	return 0;
}