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package class48;
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public class Problem_0499_TheMazeIII {
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// 节点：来到了哪？(r,c)这个位置
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// 从哪个方向来的！d -> 0 1 2 3 4
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// 之前做了什么决定让你来到这个位置。
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public static class Node {
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public int r;
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public int c;
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public int d;
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public String p;
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public Node(int row, int col, int dir, String path) {
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r = row;
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c = col;
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d = dir;
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p = path;
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}
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}
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public static String findShortestWay(int[][] maze, int[] ball, int[] hole) {
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int n = maze.length;
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int m = maze[0].length;
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Node[] q1 = new Node[n * m], q2 = new Node[n * m];
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int s1 = 0, s2 = 0;
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boolean[][][] visited = new boolean[maze.length][maze[0].length][4];
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s1 = spread(maze, n, m, new Node(ball[0], ball[1], 4, ""), visited, q1, s1);
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while (s1 != 0) {
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for (int i = 0; i < s1; i++) {
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Node cur = q1[i];
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if (hole[0] == cur.r && hole[1] == cur.c) {
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return cur.p;
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}
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s2 = spread(maze, n, m, cur, visited, q2, s2);
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}
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Node[] tmp = q1;
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q1 = q2;
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q2 = tmp;
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s1 = s2;
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s2 = 0;
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}
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return "impossible";
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}
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public static int[][] to = { { 1, 0 }, { 0, -1 }, { 0, 1 }, { -1, 0 }, { 0, 0 } };
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public static String[] re = { "d", "l", "r", "u" };
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// maze迷宫，走的格子
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// n 行数
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// m 列数
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// 当前来到的节点，cur -> (r,c) 方向 路径（决定）
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// v [行][列][方向] 一个格子，其实在宽度有限遍历时，是4个点！
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// q 下一层的队列
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// s 下一层队列填到了哪，size
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// 当前点cur，该分裂分裂，该继续走继续走，所产生的一下层的点，进入q，s++
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// 返回值：q增长到了哪？返回size -> s
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public static int spread(int[][] maze, int n, int m,
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Node cur, boolean[][][] v, Node[] q, int s) {
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int d = cur.d;
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int r = cur.r + to[d][0];
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int c = cur.c + to[d][1];
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// 分裂去！
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if (d == 4 || r < 0 || r == n || c < 0 || c == m || maze[r][c] != 0) {
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for (int i = 0; i < 4; i++) {
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if (i != d) {
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r = cur.r + to[i][0];
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c = cur.c + to[i][1];
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if (r >= 0 && r < n && c >= 0 && c < m && maze[r][c] == 0 && !v[r][c][i]) {
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v[r][c][i] = true;
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Node next = new Node(r, c, i, cur.p + re[i]);
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q[s++] = next;
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}
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}
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}
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} else { // 不分裂！继续走！
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if (!v[r][c][d]) {
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v[r][c][d] = true;
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q[s++] = new Node(r, c, d, cur.p);
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}
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}
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return s;
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}
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}
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