2019初赛 E 迷宫

http://oj.ecustacm.cn/problem.php?id=1455

s数值不能设为）0x3f，如果设为它，机器跑不出来，具体我也不知道为什么

再一个，这个题dfs跑不出来，所以提交答案

dfs

#include <bits/stdc++.h>
using namespace std;
char a;
int mp[40][60];
int vis[40][60],step[40][60];
string ans;
int s =9999999;// 0x3f;
int v[10000];
int dp[4][2] ={{1,0},{0,-1},{0,1},{-1,0}};
int dir[4] = {'D','L','R','U'};
void dfs(int x,int y,int sp){
    if(s < sp)
        return;
    if(x == 29 && y == 49){
        if(s > sp){
            s = sp;
            ans = "";
            for(int i = 1; i < sp; i++)
                ans += dir[v[i]];
        }
        return;
    }
    for(int i = 0; i < 4; i++){
        int dx = x + dp[i][0];
        int dy = y + dp[i][1];
        if(dx < 0 || dx > 29 || dy < 0 || dy > 49)
            continue;
        if(vis[dx][dy] || mp[dx][dy])
            continue;
        if(sp + 1 > step[dx][dy])
            return;
        step[dx][dy] = sp + 1;
        vis[dx][dy] = 1;
        v[sp] = i;
        dfs(dx,dy,sp + 1);
        vis[dx][dy] = 0;
    }
}
int main(){
    //freopen("in","r",stdin);
    ios::sync_with_stdio(0);
    memset(step,0x3f, sizeof(step));
    for(int i = 0; i < 30; i++){
        for(int j = 0; j < 50; j++){
            cin >> a;
            mp[i][j] = a - '0';
        }
    }
    vis[0][0] = 1;
    dfs(0,0,1);
    cout << ans << endl;
//cout << "DDDDRRURRRRRRDRRRRDDDLDDRDDDDDDDDDDDDRDDRRRURRUURRDDDDRDRRRRRRDRRURRDDDRRRRUURUUUUUUULULLUUUURRRRUULLLUUUULLUUULUURRURRURURRRDDRRRRRDDRRDDLLLDDRRDDRDDLDDDLLDDLLLDLDDDLDDRRRRRRRRRDDDDDDRR";
    return 0;
}