90分求助

#include<bits/stdc++.h>
using namespace std;
int n, m, k, yu[3010][3010], vis[3010][3010], h[3010][3010], flag;
struct node{
	int s, t, bu;
};
inline int read(){
	int x=0,f=1;
	char c=getchar();
	while(c<'0'||c>'9'){
		if(c=='-')f=-1;
		c=getchar();
	}
	while(c>='0'&&c<='9'){
		x=(x<<3)+(x<<1)+(c^48);
		c=getchar();
	}
	return x*f;
}
bool operator < (const node &a, const node &b){
	return a.bu > b.bu;
}
priority_queue<node> q;
void bfs(){
	q.push((node){1, 1, 0});
	while(!q.empty()){
		int a = q.top().s, b = q.top().t, bu = q.top().bu;
		q.pop();
		if(a == n && b == m){
			cout << bu;
			exit(0);
		} 
		if(vis[a][b]){
			continue;
		}
		vis[a][b] = 1;
		int dir[4][2] = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}};
		for(int i = 0;i < 4;i++){
			int aa = a + dir[i][0], bb = b + dir[i][1];
			if(!vis[aa][bb] && h[aa][bb] && aa >= 1 && bb >= 1 && aa <= n && bb <= m){
				q.push((node){aa, bb, bu + 1});
			} 
		}
		if(flag == 0 && yu[a][b]){
			for(int i = 1;i <= n;i++){
				for(int j = 1;j <= m;j++){
					if((i != a || j != b) && yu[i][j]){
						if(h[i][j] == h[a][b])
							q.push((node){i, j, bu + 1});
						else 
							q.push((node){i, j, bu + 2});
					}
				}
			}
			flag = 1;
		}
	}
}
int main(){
	n = read(), m = read(), k = read();
	for(int i = 1;i <= n;i++){
		for(int j = 1;j <= m;j++){
			h[i][j] = read();
		}
	}
	while(k--){
		int x, y;
		x = read(), y = read();
		yu[x][y] = 1;
	}
	bfs();
	puts("-1");
}