Add solution 25.

Author: javadev

src/Algorithms/0025.reverse-nodes-in-k-group/reverse-nodes-in-k-group.php

@@ -0,0 +1,49 @@
+/**
+ * Definition for a singly-linked list.
+ * class ListNode {
+ *     public $val = 0;
+ *     public $next = null;
+ *     function __construct($val) { $this->val = $val; }
+ * }
+ */
+class Solution {
+
+    /**
+     * @param ListNode $head
+     * @param Integer $k
+     * @return ListNode
+     */
+    function reverseKGroup($head, $k) {
+        if($head==null || $k<2){
+            return $head;
+        }
+
+        $temp = null;
+        $curr = $head;
+        $prev = null;
+        $count = 0;
+        
+        while($count<$k && $curr!=null){
+            $temp = $curr->next;
+            $curr->next = $prev;
+            $prev = $curr;
+            $curr = $temp;
+            $count++;
+        }
+        
+        if($count<$k){
+            while($count!=0){
+                $temp = $prev->next;
+                $prev->next = $curr;
+                $curr = $prev;
+                $prev = $temp;
+                $count--;
+            }
+            return $curr;
+        }
+        
+        $head->next = self::reverseKGroup($curr,$k);
+        
+        return $prev;
+    }
+}