蓝桥T291（BFS + 输出路径）

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <queue>
 5 #include <algorithm>
 6 using namespace std;
 7 const int INF = 0x3f3f3f3f;
 8 char direct[4] = {‘D‘,‘L‘,‘R‘,‘U‘},path[10000];
 9 int n,m,dis[600][600],cnt;
10 int gx[4] = {1,0,0,-1};
11 int gy[4] = {0,-1,1,0};
12 char g[600][600];
13 struct point
14 {
15     int x,y;
16 };
17 void bfs(int x,int y)
18 {
19     queue<point> q;
20     point temp,temp2;
21     temp.x = x;
22     temp.y = y;
23     q.push(temp);
24     while(q.size())
25     {
26         temp2 = q.front();
27         q.pop();
28         if(temp2.x == n && temp2.y == m)
29         {
30             return;
31         }
32         for(int i = 0; i < 4; i++)
33         {
34             int fx = gx[i] + temp2.x;
35             int fy = gy[i] + temp2.y;
36             if(fx >= 1 && fx <= n && fy >= 1 && fy <= m && g[fx][fy] == ‘0‘ && dis[fx][fy] > dis[temp2.x][temp2.y] + 1)
37             {
38                 dis[fx][fy] = dis[temp2.x][temp2.y] + 1;
39                 temp.x = fx;
40                 temp.y = fy;
41                 q.push(temp);
42             }
43         }
44     }
45 }
46 int dfs(int x,int y,int ans)
47 {
48     if(x == n && y == m)
49     {
50         cnt = ans;
51         return true;
52     }
53     for(int i = 0; i < 4; i++)
54     {
55         int fx = x + gx[i];
56         int fy = y + gy[i];
57         if(fx >= 1 && fx <= n && fy <= m && fy >= 1 && dis[x][y] + 1 == dis[fx][fy])
58         {
59             path[ans] = direct[i];
60             if(dfs(fx,fy,ans + 1)) //不满足要回溯！
61                 return true;
62         }
63     }
64     return false;
65 }
66 int main()
67 {
68     scanf("%d%d", &n, &m);
69     getchar();
70     for(int i = 1; i <= n; i++)
71     {
72         for(int j = 1; j <= m; j++)
73         {
74             scanf("%c", &g[i][j]);
75         }
76         getchar();
77     }
78     memset(dis, INF, sizeof(dis));
79     dis[1][1] = 0;
80     cnt = 0;
81     bfs(1,1);
82     dfs(1,1,0);
83     printf("%d\n", dis[n][m]);
84     path[cnt] = ‘\0‘;
85     printf("%s\n", path);
86    return 0;
87 }