Merge pull request chipbk10#91 from chipbk10/Graph

Solve Problem 864 - Shortest Path To Get All Keys

Author: chipbk10

README.md

@@ -12,7 +12,7 @@
 ### Trie:
 ### Binary Search: [#](https://leetcode.com/discuss/interview-question/313216/)
 ### Minimax: 913
-### Matrix: 1368, 1292
+### Matrix: 1368, 1292, 864
 
 # Favorite: 
 

src/contest/ReadMe.java

@@ -18,9 +18,9 @@ public class ReadMe {
     // sliding window:      1208[v]     1040[!]     995[!]
     // linked-list:         1290[v]     1019[!]     876[v]
     // union-find:          1202[v]     924[v]      947[!]
-    // heap:                1054[!]     882[!]      864
-    // design:              1352[x]     1348[x]     705
-    // bit manipulation:    1356[v]     1342[v]     1318
+    // heap:                1054[!]     882[!]      864[x]
+    // design:              1352[x]     1348[x]     705[v]
+    // bit manipulation:    1356[v]     1342[v]     1318[v]
     // other:               913[x]      1288[v]     843
 
 

src/graph/bfs/Problem864_ShortestPathToGetAllKeys.java

@@ -0,0 +1,51 @@
+package graph.bfs;
+
+import java.util.HashSet;
+import java.util.LinkedList;
+import java.util.Queue;
+import java.util.Set;
+
+public class Problem864_ShortestPathToGetAllKeys {
+
+
+    // STILL WRONG
+    public int shortestPathAllKeys(String[] A) {
+        int m = A.length, n = A[0].length(), KEYS = 0;
+        Set<Integer> seen = new HashSet<>();
+        Queue<int[]> queue = new LinkedList<>();
+
+        for (int i = 0; i < m; i++) {
+            for (int j = 0; j < n; j++) {
+                char c = A[i].charAt(j);
+                if (c == '@') {
+                    queue.offer(new int[] {i, j, 0});
+                    seen.add((i*m+j) * 127 + 0);
+                }
+                else if (c >= 'a' && c <= 'f') KEYS |= (1 << (c-'a'));
+            }
+        }
+
+        int dirs[][] = {{-1, 0}, {0, -1}, {1, 0}, {0, 1}}, res = -1;
+        while (!queue.isEmpty()) {
+            res++;
+            int size = queue.size();
+            for (int k = 0; k < size; k++) {
+                int e[] = queue.poll(), i = e[0], j = e[1], keys = e[2];
+                for (int[] d : dirs) {
+                    int x = i + d[0], y = j + d[1];
+                    if (x < 0 || x >= m || y < 0 || y >= n) continue;                   // out of grid
+                    char c = A[x].charAt(y);
+                    if (seen.contains((x*m+y)*127 + keys)) continue;                    // visited
+                    if (c == '#') continue;                                             // wall
+                    if (c >= 'A' && c <= 'F' && (keys & (1 << (c-'A'))) == 0) continue; // no key
+                    if (c >= 'a' && c <= 'f') keys |= (1 << (c-'a'));                   // update key
+                    if (keys == KEYS) return res;
+                    queue.offer(new int[] {x, y, keys});
+                    seen.add((x*m+y)*127 + keys);
+                }
+            }
+        }
+
+        return -1; // not found
+    }
+}