HDU 2821 Pusher

dfs

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <vector>
#include <map>
#include <queue>
#include <ctime>
#include <set>
#define ll long long
#define MK make_pair
#define PB push_back
#define SZ(x) ((int)(x).size())
#define FOR(it,c) for ( __typeof((c).begin()) it=(c).begin(); it!=(c).end(); it++ )
using namespace std;

char g[30][30];
string op="UDLR",ansop;
int sum=0,a[30][30],n,m,ansx,ansy,nn,dx[]={-1,1,0,0},dy[]={0,0,-1,1};
bool ok;

inline bool in(int x,int y){
    return x<n&&x>=0&&y<m&&y>=0;
}

void dfs(int x,int y,int cnt,int ind,string opp){
    if(!cnt){
        nn=ind;
        ok=true;
        ansop=opp;
        return;
    }
    if(ok) return;
    for(int i=0;i<4;i++){
        int nx=x+dx[i],ny=y+dy[i];
        if(!in(nx,ny)||a[nx][ny]) continue;
        while(in(nx,ny)&&!a[nx][ny]) nx+=dx[i],ny+=dy[i];
        if(!in(nx,ny)) continue;
        int t=a[nx][ny];
        a[nx][ny]=0;
        if(!in(nx+dx[i],ny+dy[i])) dfs(nx,ny,cnt-t,ind+1,opp+op[i]);
        else{
            a[nx+dx[i]][ny+dy[i]]+=t-1;
            dfs(nx,ny,cnt-1,ind+1,opp+op[i]);
        }
        a[nx][ny]=t;
        if(in(nx+dx[i],ny+dy[i])) a[nx+dx[i]][ny+dy[i]]-=t-1;
    }
}

int main(){
#ifndef ONLINE_JUDGE
    freopen("a.in","r",stdin);
    freopen("a.out","w",stdout);
#endif
    while(cin>>m>>n){
        for(int i=0;i<n;i++) scanf("%s",g[i]);
        sum=0;ansop="";
        for(int i=0;i<n;i++) 
            for(int j=0;j<m;j++){
                if(g[i][j]=='.') a[i][j]=0;
                else a[i][j]=g[i][j]-'a'+1;
                sum+=a[i][j];
            }
        ok=false;
        for(int i=0;i<n;i++){
            for(int j=0;j<m;j++)
                if(g[i][j]=='.'){
                    dfs(i,j,sum,0,"");
                    if(ok){
                        ansx=i;ansy=j;
                        break;
                    }
                }
            if(ok) break;
        }
        cout<<ansx<<endl;
        cout<<ansy<<endl;
        cout<<ansop<<endl;
    }
    return 0;
}