Add solution 864.

Author: javadev

src/Algorithms/0864.shortest-path-to-get-all-keys/shortest-path-to-get-all-keys.php

@@ -0,0 +1,76 @@
+class Status {
+    var $key;
+    var $i;
+    var $j;
+    function __construct($key, $i, $j) {
+        $this->key = $key;
+        $this->i = $i;
+        $this->j = $j;
+    }
+}
+
+class Solution {
+
+    /**
+     * @param String[] $grid
+     * @return Integer
+     */
+    function shortestPathAllKeys($grid) {
+        $success = 0;
+        $startI = 0;
+        $startJ = 0;
+        $rows = count($grid);
+        $cols = strlen($grid[0]);
+        for ($i = 0; $i < $rows; $i++) {
+            for ($j = 0; $j < $cols; $j++) {
+                $c = $grid[$i][$j];
+                if ($c >= 'A' && $c <= 'F') {
+                    $success |= 1 << (ord($c) - ord('A'));
+                }
+                
+                if ($c == '@') {
+                    $startI = $i;
+                    $startJ = $j;
+                }
+            }
+        }
+        $dist = array_fill(0, 1 << 6, array_fill(0, $rows, array_fill(0, $cols, 2147483647)));
+        $queue = [];
+        array_push($queue, new Status(0, $startI, $startJ));
+        $dist[0][$startI][$startJ] = 0;
+        $path = 0;
+        $dirs = [[-1, 0], [0, 1], [1, 0], [0, -1]];
+        while (!empty($queue)) {
+            $size = count($queue);
+            while ($size-- > 0) {
+                $status = array_pop($queue);
+                $key = $status->key;
+                $x = $status->i;
+                $y = $status->j;
+                if ($key == $success) return $path;
+                foreach ($dirs as $dir) {
+                    $xx = $x + $dir[0];
+                    $yy = $y + $dir[1];
+                    if ($xx >= 0 && $xx < $rows && $yy >= 0 && $yy < $cols && $grid[$xx][$yy] != '#') {
+                        $nextKey = $key;
+                        $c = $grid[$xx][$yy];
+                        if ($c >= 'a' && $c <= 'f') {
+                            $nextKey = $key | (1 << (ord($c) - ord('a')));
+                        }
+                        
+                        if ($c >= 'A' && $c <= 'F') {
+                            if (($nextKey & (1 << (ord($c) - ord('A')))) == 0) continue;
+                        }
+                        
+                        if ($path + 1 < $dist[$nextKey][$xx][$yy]) {
+                            $dist[$nextKey][$xx][$yy] = $path + 1;
+                            array_unshift($queue, new Status($nextKey, $xx, $yy));
+                        }
+                    }
+                }
+            }
+            $path++;
+        }
+        return -1;
+    }
+}