90pts bfs做法 #2TLE

#include<bits/stdc++.h>
using namespace std;

int n,m,ans=1;
int maps[105][105];
bool vis[105][105];
int go[4][2]={{1,0},{-1,0},{0,1},{0,-1}};

struct xy{
	int x,y;
};

struct node{
	int x,y,dist;
	vector<xy>was;
}; 

void bfs(int firsx,int firsy){
	queue<node>q;
	node t1,t2;
	t1.dist=1;
	t1.x=firsx;
	t1.y=firsy;
	vector<xy>p;
	xy w;w.x=t1.x;
	w.y=t1.y;
	p.push_back(w);
	t1.was=p;
	vis[firsx][firsy]=1;
	q.push(t1);
	
	while (!q.size()==0){
		t1=q.front();
//		printf("[debug]x=%d y=%d dist=%d ans=%d\n",t1.x,t1.y,t1.dist,ans);
//		for (int i=0;i<t1.was.size();++i)cout<<t1.was[i].x<<' '<<t1.was[i].y<<" | ";
//		cout<<endl<<endl;
		for (int i=0;i<4;++i){
			int nx=t1.x+go[i][0];
			int ny=t1.y+go[i][1];
			int ndist=t1.dist+1;
			xy t;t.x=nx;t.y=ny;
			if (nx>=1&&nx<=n&&ny>=1&&ny<=m&&vis[nx][ny]==0&&maps[nx][ny]<maps[t1.x][t1.y]){
				t2.was=t1.was;
				t2.was.push_back(t);
				t2.x=nx;
				t2.y=ny;
				t2.dist=ndist;
				q.push(t2);
				ans=max(ans,t2.dist);
			}
		}
		vis[t1.x][t1.y]=0;
		q.pop();
	}
	return ;
}

int main(){
	cin>>n>>m;
	for (int i=1;i<=n;++i){
		for (int j=1;j<=m;++j){
			cin>>maps[i][j];
		}
	} 
	
	for (int i=1;i<=n;++i){
		for (int j=1;j<=m;++j){
			bfs(i,j);
		}
	}
	cout<<ans;
	return 0;
}
/*
5 5
1 2 3 4 5
16 17 18 19 6
15 24 25 20 7
14 23 22 21 8
13 12 11 10 9

*/