Shared code

/*
   Three things which are very important --
   Violence - Speed - Momentum
*/
#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#define oset tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update>
#define setbits(x)      __builtin_popcountll(x)
#define leadzero(x)     __builtin_clz(x)
#define trailzero(x)    __builtin_ctz(x)
#define bitsparity(x)   __builtin_parity(x)
#define mod             1000000007
#define FIO             ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define ll              long long 
#define pre(y,x)        fixed<<setprecision(y)<<x
#define dbg1(x)         cerr << "|" << #x << ": " << (x) << "|\n";
#define dbg2(x,y)       cerr << "|" << #x << ": " << (x) << "|" << #y << ": " << (y) << "|\n";
#define dbg3(x,y,z)     cerr << "|" << #x << ": " << (x) << "|" << #y << ": " << (y) << "|" << #z << ": " << (z) << "|\n";
#define ff              first
#define ss              second
#define pb              push_back
#define eb              emplace_back
#define popb            pop_back
#define endl            '\n'
#define all(v)          v.begin(), v.end()
#define sz(x)           ((int)((x).size()))
typedef pair<int, int> pii; 
typedef pair<ll, ll> pll; 
typedef pair<string, string> pss; 
typedef vector<int> vi; 
typedef vector<vi> vvi; 
typedef vector<pii> vii;
typedef vector<pll> vll; 
typedef vector<ll> vl; 
typedef vector<vl> vvl;
typedef vector<string> vs;
ll power(ll a, ll b) {
	if(b<0) return 1;
	ll res=1;
	while(b) {
		if(b&1) 
			res = (res*a)%mod;
		a = (a*a)%mod;
		b >>= 1;
	}
	return res;
}
bool ispoweroftwo(ll x){ return (x&&!(x&(x-1)));}
inline ll gcd(ll a, ll b) {ll r; while (b) {r = a % b; a = b; b = r;} return a;}
inline ll lcm(ll a, ll b) {return a / gcd(a, b) * b;}
const int inf = 1e9;
int dx[] = {-1, 0, 1, 0}; 
int dy[] = {0, 1, 0, -1};
char PH[] = {'U', 'R', 'D', 'L'};
//integer to char always remember (char+'0')
const double pi = acos(-1);
const ll INF = 1e18;
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
const int mxN = 2e3+9;
//vector<ll> adj[mxN];
int vis[mxN][mxN];
vector<string> v(mxN);
int  n, m;
vector<vector<string>> path(mxN, vector<string>(mxN));
pair<ll, ll> a, b;
void bfs(int i, int j) {
	vis[i][j] = 1;
	queue<pair<ll, ll>> q;
	q.push({i ,j});

	while(!q.empty()) {
		pair<ll, ll> p = q.front();
		q.pop();
		vis[p.ff][p.ss] = 1;
		for(int i=0; i<4; ++i) {
			int x = p.ff + dx[i];
			int y = p.ss + dy[i];
			
			if(x<0 || x>=n || y<0 || y>=m || v[x][y] == '#') continue;
			if(!vis[x][y]) {
				
				vis[x][y] = 1;
				q.push({x, y});
				path[x][y] = path[p.ff][p.ss]+PH[i];
			}
//			if(b.ff == x && b.ss == y) return;
		}		
	}
}
int main() {
	FIO;
	cin >> n >> m;
	
	for(int i=0; i<n; ++i) {
		cin >> v[i];
	}
	for(int i=0; i<n; ++i) {
		for(int j=0; j<m; ++j) {
			if(v[i][j] == 'A') a={i, j};
			else if(v[i][j] == 'B') b={i, j};
		}
	}
	bfs(a.ff, a.ss);
	
	if(vis[b.ff][b.ss]) {
		string rev = path[b.ff][b.ss];
		cout << "YES\n" << sz(rev) << "\n" << rev;
	} else {
		cout << "NO";
	}
	return 0;	
}
/*	
3 3
A..
###
#.B
*/