19年第十届蓝桥杯第三题

#include <cstring>
#include <iostream>
#include <algorithm>
#include <set>
#include <queue>

using namespace std;

const int N = 55;

int n, m;
string g[N];
int dist[N][N];
int dx[4] = {1, 0, 0, -1}, dy[4] = {0, -1, 1, 0};
char dir[4] = {'D', 'L', 'R', 'U'};

void bfs()
{

queue<pair<int,int>> q;
memset(dist, -1, sizeof dist);
dist[n - 1][m - 1] = 0;
q.push({n - 1, m - 1});
while (q.size())
{
auto t = q.front();
q.pop();

for (int i = 0; i < 4; i ++ )
{
int x = t.first + dx[i], y = t.second + dy[i];
if (x >= 0 && x < n && y >= 0 && y < m && dist[x][y] == -1 && g[x][y] == '0')
{
dist[x][y] = dist[t.first][t.second] + 1;
q.push({x, y});
}
}
}
}

int main()
{
cin >> n >> m;
for (int i = 0; i < n; i ++ ) cin >> g[i];

bfs();

cout << dist[0][0] << endl;

int x = 0, y = 0;
string res;
while (x != n - 1 || y != m - 1)
{
for (int i = 0; i < 4; i ++ )
{
int nx = x + dx[i], ny = y + dy[i];
if (nx >= 0 && nx < n && ny >= 0 && ny < m && g[nx][ny] == '0')
{
if (dist[x][y] == 1 + dist[nx][ny])
{
x = nx, y = ny;
res += dir[i];
break;
}
}
}
}

cout << res << endl;

return 0;
}

作者：yxc
来源：AcWing