Merge pull request #2473 from cn-hideyoshi/master

Update 0203.移除链表元素.md- 修改php解法,原解法非php

problems/0203.移除链表元素.md

@@ -497,27 +497,67 @@ func removeElements(_ head: ListNode?, _ val: Int) -> ListNode? {
 
 ```php
 /**
- * Definition for singly-linked list.
- * type ListNode struct {
- *     Val int
- *     Next *ListNode
+ * Definition for a singly-linked list.
+ * class ListNode {
+ *     public $val = 0;
+ *     public $next = null;
+ *     function __construct($val = 0, $next = null) {
+ *         $this->val = $val;
+ *         $this->next = $next;
+ *     }
  * }
  */
- // 虚拟头+双指针
-func removeElements(head *ListNode, val int) *ListNode {
-    dummyHead := &ListNode{}
-    dummyHead.Next = head
-    pred := dummyHead
-    cur := head
-    for cur != nil {
-        if cur.Val == val {
-            pred.Next = cur.Next
+
+//版本一（在原链表上直接删除）：
+class Solution {
+
+    /**
+     * @param ListNode $head
+     * @param Integer $val
+     * @return ListNode
+     */
+    function removeElements($head, $val)
+    {
+  	if ($head == null) {
+            return null;
+        }
+
+        $now = $head;
+        while ($now->next != null) {
+            if ($now->next->val == $val) {
+                $now->next = $now->next->next;
             } else {
-            pred = cur
+                $now = $now->next;
             }
-        cur = cur.Next
         }
-    return dummyHead.Next
+        if ($head->val == $val) {
+            return $head->next;
+        }
+        return $head;
+    }
+}
+
+//版本二（虚拟头结点方式）：
+class Solution {
+
+    /**
+     * @param ListNode $head
+     * @param Integer $val
+     * @return ListNode
+     */
+    function removeElements($head, $val)
+    {
+        $dummyHead = new ListNode(0, $head);
+        $now = $dummyHead;
+        while ($now->next != null){
+            if ($now->next->val == $val) {
+                $now->next = $now->next->next;
+            } else {
+                $now = $now->next;
+            }
+        }
+        return $dummyHead->next;
+    }
 }
 ```