【HDOJ】1983 Kaitou Kid - The Phantom Thief (2)
不仅仅是DFS，还需要考虑可以走到终点。同时，需要进行预处理。至多封闭点数为起点和终点的非墙壁点的最小值。
1 #include <iostream> 2 #include <cstdio> 3 #include <cstring> 4 #include <cstdlib> 5 #include <queue> 6 using namespace std; 7 8 typedef struct node_st { 9 int x, y, t, flg; 10 node_st() {} 11 node_st(int xx, int yy, int tt, int fflg) { 12 x=xx; y=yy; t=tt; flg=fflg; 13 } 14 } node_st; 15 16 char map[10][10]; 17 char visit[10][10][2]; 18 int direct[4][2] = {{-1,0},{1,0},{0,-1},{0,1}}; 19 int n, m, time, fmin; 20 int begx, begy, endx, endy; 21 22 bool check(int x, int y) { 23 if (x<0 || x>=n || y<0 || y>= m) 24 return false; 25 return true; 26 } 27 28 bool bfs() { 29 queue<node_st> que; 30 int x, y, t, flg; 31 int i; 32 node_st node; 33 34 memset(visit, 0, sizeof(visit)); 35 que.push(node_st(begx, begy, 0, 0)); 36 visit[begx][begy][0] = 1; 37 38 while ( !que.empty() ) { 39 node = que.front(); 40 que.pop(); 41 t = node.t; 42 if (t == time) 43 break; 44 for (i=0; i<4; ++i) { 45 x = node.x + direct[i][0]; 46 y = node.y + direct[i][1]; 47 flg = node.flg; 48 if ( !check(x, y) ) 49 continue; 50 if (map[x][y] != '#') { 51 if (map[x][y] == 'E' && flg==1) 52 return true; 53 if (map[x][y] == 'J') 54 flg = 1; 55 if (t<time && !visit[x][y][flg]) { 56 visit[x][y][flg] = 1; 57 que.push(node_st(x, y, t+1, flg)); 58 } 59 } 60 } 61 } 62 63 return false; 64 } 65 66 void printmap() { 67 for (int i=0; i<n; ++i) 68 printf("\t%s\n", map[i]); 69 } 70 71 int dfs(int t, int cur) { 72 int flg = 0; 73 char ch; 74 75 if (t >= fmin) 76 return 0; 77 78 for (int i=0; i<n; ++i) { 79 for (int j=0; j<m; ++j) { 80 if (map[i][j]=='.' || map[i][j] == 'J') { 81 ch = map[i][j]; 82 map[i][j] = '#'; 83 if (cur == t) { 84 //printmap(); 85 if ( !bfs() ) { 86 fmin = (t<fmin) ? t:fmin; 87 return 1; 88 } 89 } 90 if (cur < t) 91 flg = dfs(t, cur+1); 92 map[i][j] = ch; 93 } 94 if (flg) 95 return 1; 96 } 97 } 98 99 return 0; 100 } 101 102 int pre() { 103 int i, x, y, tmp1, tmp2; 104 105 tmp1 = 0; 106 for (i=0; i<4; ++i) { 107 x = begx + direct[i][0]; 108 y = begy + direct[i][1]; 109 if ( check(x, y) && (map[x][y]=='.'||map[x][y]=='J')) 110 tmp1++; 111 } 112 113 tmp2 = 0; 114 for (i=0; i<4; ++i) { 115 x = endx + direct[i][0]; 116 y = endy + direct[i][1]; 117 if ( check(x, y) && (map[x][y]=='.'||map[x][y]=='J')) 118 tmp2++; 119 } 120 121 return tmp1<tmp2 ? tmp1 : tmp2; 122 } 123 124 int main() { 125 int case_n; 126 int i, j; 127 128 scanf("%d", &case_n); 129 130 while (case_n--) { 131 scanf("%d %d %d%*c", &n, &m, &time); 132 for (i=0; i<n; ++i) { 133 scanf("%s", map[i]); 134 for (j=0; j<m; ++j) { 135 if (map[i][j] == 'S') { 136 begx = i; 137 begy = j; 138 } 139 if (map[i][j] == 'E') { 140 endx = i; 141 endy = j; 142 } 143 } 144 } 145 if ( !bfs() ) { 146 printf("0\n"); 147 continue; 148 } 149 fmin = pre(); 150 //printf("pre:%d\n", fmin); 151 dfs(1,1); 152 //printf("1:%d\n", fmin); 153 dfs(2,1); 154 //printf("2:%d\n", fmin); 155 dfs(3,1); 156 printf("%d\n", fmin); 157 } 158 159 return 0; 160 }
