POJ3009 Curling 2.0

　　暴力DFS + 回溯。注意行和列不要搞反，并且当搜索深度大于10的时候直接返回。
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  1 #include <stdio.h>
  2 #include <string.h>
  3 
  4 int r, c, ans;
  5 int g[25][25];
  6 
  7 inline int min(int x, int y){return x < y ? x : y;}
  8 
  9 int checkup(int x, int y)
 10 {
 11     if(y - 1 > 0 && g[y - 1][x] == 1)
 12         return 0;
 13     int i;
 14     for(i = y - 1; i > 0; i --)
 15     {
 16         if(g[i][x] == 3)
 17             return -1;
 18         if(g[i][x] == 1)
 19         {
 20             g[i][x] = 0;
 21             return i + 1;
 22         }
 23     }
 24     return 0;
 25 }
 26 
 27 int checkdown(int x, int y)
 28 {
 29     if(y + 1 <= r && g[y + 1][x] == 1)
 30         return 0;
 31     int i;
 32     for(i = y + 1; i <= r; i ++)
 33     {
 34         if(g[i][x] == 3)
 35             return -1;
 36         if(g[i][x] == 1)
 37         {
 38             g[i][x] = 0;
 39             return i - 1;
 40         }
 41     }
 42     return 0;
 43 }
 44 
 45 int checkleft(int x, int y)
 46 {
 47     if(x - 1 > 0 && g[y][x - 1] == 1)
 48         return 0;
 49     int i;
 50     for(i = x - 1; i > 0; i --)
 51     {
 52         if(g[y][i] == 3)
 53             return -1;
 54         if(g[y][i] == 1)
 55         {
 56             g[y][i] = 0;
 57             return i + 1;
 58         }
 59     }
 60     return 0;
 61 }
 62 
 63 int checkright(int x, int y)
 64 {
 65     if(x + 1 <= c && g[y][x + 1] == 1)
 66         return 0;
 67     int i;
 68     for(i = x + 1; i <= c; i ++)
 69     {
 70         if(g[y][i] == 3)
 71             return -1;
 72         if(g[y][i] == 1)
 73         {
 74             g[y][i] = 0;
 75             return i - 1;
 76         }
 77     }
 78     return 0;
 79 }
 80 
 81 void dfs(int cx, int cy, int d)
 82 {
 83     if(d >= 10)
 84         return ;
 85     int up = checkup(cx, cy);
 86     if(up == -1)
 87     {
 88         ans = (ans == -1 ? d + 1 : min(ans, d + 1));
 89         return ;
 90     }
 91     else if(up != 0)
 92     {
 93         dfs(cx, up, d + 1);
 94         g[up - 1][cx] = 1;
 95     }
 96         
 97     int down = checkdown(cx, cy);
 98     if(down == -1)
 99     {
100         ans = (ans == -1 ? d + 1 : min(ans, d + 1));
101         return ;
102     }
103     else if(down != 0)
104     {
105         dfs(cx, down, d + 1);
106         g[down + 1][cx] = 1;
107     }
108         
109     int left = checkleft(cx, cy);
110     if(left == -1)
111     {
112         ans = (ans == -1 ? d + 1 : min(ans, d + 1));
113         return ;
114     }
115     else if(left != 0)
116     {
117         dfs(left, cy, d + 1);
118         g[cy][left - 1] = 1;
119     }
120         
121     int right = checkright(cx, cy);
122     if(right == -1)
123     {
124         ans = (ans == -1 ? d + 1 : min(ans, d + 1));
125         return ;
126     }
127     else if(right != 0)
128     {
129         dfs(right, cy, d + 1);
130         g[cy][right + 1] = 1;
131     }
132 }
133 
134 int main()
135 {
136     int i, j, sx, sy;
137     while(scanf("%d%d", &c, &r), r + c)
138     {
139         for(i = 1; i <= r; i ++)
140         {
141             for(j = 1; j <= c; j ++)
142             {
143                 scanf("%d", &g[i][j]);
144                 if(g[i][j] == 2)
145                     sx = j, sy = i;
146             }
147         }
148         ans = -1;
149         dfs(sx, sy, 0);
150         printf("%d\n", ans);
151     }
152     return 0;
153 }