Added task 864.

Author: javadev

src/main/java/g0801_0900/s0864_shortest_path_to_get_all_keys/Solution.java

@@ -0,0 +1,88 @@
+package g0801_0900.s0864_shortest_path_to_get_all_keys;
+
+import java.util.LinkedList;
+
+public class Solution {
+    class Status {
+        int key;
+        int i;
+        int j;
+
+        public Status(int key, int i, int j) {
+            this.key = key;
+            this.i = i;
+            this.j = j;
+        }
+    }
+
+    public int shortestPathAllKeys(String[] grid) {
+        int success = 0;
+        int startI = 0;
+        int startJ = 0;
+        int rows = grid.length;
+        int cols = grid[0].length();
+        for (int i = 0; i < rows; i++) {
+            for (int j = 0; j < cols; j++) {
+                char c = grid[i].charAt(j);
+                if (c >= 'A' && c <= 'F') {
+                    success |= 1 << (c - 'A');
+                }
+
+                if (c == '@') {
+                    startI = i;
+                    startJ = j;
+                }
+            }
+        }
+        int[][][] dist = new int[1 << 6][rows][cols];
+        for (int i = 0; i < dist.length; i++) {
+            for (int j = 0; j < dist[0].length; j++) {
+                for (int k = 0; k < dist[0][0].length; k++) {
+                    dist[i][j][k] = Integer.MAX_VALUE;
+                }
+            }
+        }
+        LinkedList<Status> queue = new LinkedList<>();
+        queue.offer(new Status(0, startI, startJ));
+        dist[0][startI][startJ] = 0;
+        int path = 0;
+        int[][] dirs = {{-1, 0}, {0, 1}, {1, 0}, {0, -1}};
+        while (!queue.isEmpty()) {
+            int size = queue.size();
+            while (size-- > 0) {
+                Status status = queue.poll();
+                int key = status.key;
+                int x = status.i;
+                int y = status.j;
+                if (key == success) {
+                    return path;
+                }
+                for (int[] dir : dirs) {
+                    int xx = x + dir[0];
+                    int yy = y + dir[1];
+                    if (xx >= 0
+                            && xx < rows
+                            && yy >= 0
+                            && yy < cols
+                            && grid[xx].charAt(yy) != '#') {
+                        int nextKey = key;
+                        char c = grid[xx].charAt(yy);
+                        if (c >= 'a' && c <= 'f') {
+                            nextKey = key | (1 << (c - 'a'));
+                        }
+
+                        if (c >= 'A' && c <= 'F' && (nextKey & (1 << (c - 'A'))) == 0) {
+                            continue;
+                        }
+                        if (path + 1 < dist[nextKey][xx][yy]) {
+                            dist[nextKey][xx][yy] = path + 1;
+                            queue.offer(new Status(nextKey, xx, yy));
+                        }
+                    }
+                }
+            }
+            path++;
+        }
+        return -1;
+    }
+}

src/test/java/g0801_0900/s0864_shortest_path_to_get_all_keys/SolutionTest.java

@@ -0,0 +1,18 @@
+package g0801_0900.s0864_shortest_path_to_get_all_keys;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import org.junit.Test;
+
+public class SolutionTest {
+    @Test
+    public void shortestPathAllKeys() {
+        Solution solution = new Solution();
+        assertThat(
+                solution.shortestPathAllKeys(new String[] {"@.a.#", "###.#", "b.A.B"}), equalTo(8));
+        assertThat(
+                solution.shortestPathAllKeys(new String[] {"@..aA", "..B#.", "....b"}), equalTo(6));
+        assertThat(solution.shortestPathAllKeys(new String[] {"@Aa"}), equalTo(-1));
+    }
+}