带记录方向的DFS

#include<bits/stdc++.h>
using namespace std;
#define ioio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define endl "\n"
#define debug(x) cout<<#x<<":"<<x<<endl;
#define L(k) k<<1
#define R(k) k<<1|1
#define P pair
#define P1 first
#define P2 second
#define u_map unordered_map
#define p_queue priority_queue
typedef long long ll;
const double eps = 1e-6;
const int mod = 1e9 + 7;
const int INF = 0x3f3f3f3f;
const int INF2 = (1 << 31);
const int N = 2e2 + 7;
int dx[] = {1, 0, -1, 0}, dy[] = {0, -1, 0, 1};
/*-------------------------------------------------*/

int n,m;
int ma[N][N];
bool vis[N][N];
vector<int>v;

void dfs(int x,int y,int pre){
	v.push_back(ma[x][y]);
	vis[x][y]=1;
	for(int i=pre,flag=0;i<=4;i++){
		if(flag==1&&i==4)break;
		else if(i==4){
			i=0;
			flag=1;
		}
		int xx=x+dx[i];
		int yy=y+dy[i];
		if(xx>=1&&xx<=n&&yy>=1&&yy<=m&&vis[xx][yy]==0){
			dfs(xx,yy,i);
			break;
		}
	}
}
void slove() {
	cin>>n>>m;
	for(int i=1;i<=n;i++)
		for(int j=1;j<=m;j++)
			cin>>ma[i][j];
	dfs(1,1,0);
	for(int x:v)
		cout<<x<<" ";
}
int main() {
	ioio
	int t=1;
	//freopen("./test.txt","r",stdin);
	//cin>>t;
	while(t--)
		slove();
	return 0;
}