ural 1145. Rope in the Labyrinth

  1 /**
  2 Create By yzx - stupidboy
  3 */
  4 #include <cstdio>
  5 #include <cstring>
  6 #include <cstdlib>
  7 #include <cmath>
  8 #include <deque>
  9 #include <vector>
 10 #include <queue>
 11 #include <iostream>
 12 #include <algorithm>
 13 #include <map>
 14 #include <set>
 15 #include <ctime>
 16 #include <iomanip>
 17 using namespace std;
 18 typedef long long LL;
 19 typedef double DB;
 20 #define MIT (2147483647)
 21 #define INF (1000000001)
 22 #define MLL (1000000000000000001LL)
 23 #define sz(x) ((int) (x).size())
 24 #define clr(x, y) memset(x, y, sizeof(x))
 25 #define puf push_front
 26 #define pub push_back
 27 #define pof pop_front
 28 #define pob pop_back
 29 #define ft first
 30 #define sd second
 31 #define mk make_pair
 32 
 33 inline int Getint()
 34 {
 35     int Ret = 0;
 36     char Ch = ‘ ‘;
 37     bool Flag = 0;
 38     while(!(Ch >= ‘0‘ && Ch <= ‘9‘))
 39     {
 40         if(Ch == ‘-‘) Flag ^= 1;
 41         Ch = getchar();
 42     }
 43     while(Ch >= ‘0‘ && Ch <= ‘9‘)
 44     {
 45         Ret = Ret * 10 + Ch - ‘0‘;
 46         Ch = getchar();
 47     }
 48     return Flag ? -Ret : Ret;
 49 }
 50 
 51 const int N = 1010;
 52 const int DX[] = {-1, 0, 1, 0}, DY[] = {0, -1, 0, 1};
 53 int n, m;
 54 char graph[N][N];
 55 int dp[N][N];
 56 queue<pair<int, int> > que;
 57 
 58 inline void Input()
 59 {
 60     scanf("%d%d", &m, &n);
 61     for(int i = 0; i < n; i++) scanf("%s", graph[i]);
 62 }
 63 
 64 inline bool Check(int x, int y)
 65 {
 66     if(x < 0 || y < 0 || x >= n || y >= m) return 0;
 67     if(graph[x][y] != ‘.‘) return 0;
 68     return 1;
 69 }
 70 
 71 inline void Bfs(int sx, int sy)
 72 {
 73     for(int i = 0; i < n; i++)
 74         for(int j = 0; j < m; j++)
 75             dp[i][j] = INF;
 76     que.push(mk(sx, sy));
 77     dp[sx][sy] = 0;
 78     while(sz(que))
 79     {
 80         int ux = que.front().ft, uy = que.front().sd;
 81         que.pop();
 82         for(int t = 0; t < 4; t++)
 83         {
 84             int vx = ux + DX[t], vy = uy + DY[t];
 85             if(Check(vx, vy) && dp[vx][vy] > dp[ux][uy] + 1)
 86             {
 87                 dp[vx][vy] = dp[ux][uy] + 1;
 88                 que.push(mk(vx, vy));
 89             }
 90         }
 91     }
 92 }
 93 
 94 inline void GetMax(int &px, int &py)
 95 {
 96     int mx = -INF;
 97     for(int i = 0; i < n; i++)
 98         for(int j = 0; j < m; j++)
 99             if(mx < dp[i][j] && dp[i][j] < INF)
100             {
101                 mx = dp[i][j];
102                 px = i, py = j;
103             }
104 }
105 
106 inline void Solve()
107 {
108     bool flag = 0;
109     for(int i = 0; i < n && !flag; i++)
110         for(int j = 0; j < m && !flag; j++)
111             if(graph[i][j] == ‘.‘)
112             {
113                 Bfs(i, j);
114                 flag = 1;
115             }
116 
117     int px, py;
118     GetMax(px, py);
119     Bfs(px, py);
120 
121     GetMax(px, py);
122     printf("%d\n", dp[px][py]);
123 }
124 
125 int main()
126 {
127     freopen("a.in", "r", stdin);
128     Input();
129     Solve();
130     return 0;
131 }