add cpp solution

Author: zouwx2cs

solution/0086.Partition List/Solution.cpp

@@ -0,0 +1,34 @@
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode(int x) : val(x), next(NULL) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* partition(ListNode* head, int x) {
+        ListNode headSmaller(0), headBigger(0) ;
+        ListNode *pSmaller = &headSmaller ;
+        ListNode *pBigger = &headBigger ;
+        ListNode *p = head ;
+        while (nullptr != p)
+        {
+            if (p->val < x)
+            {
+                pSmaller->next = p ;
+                pSmaller = p ;
+            }
+            else
+            {
+                pBigger->next = p ;
+                pBigger = p ;
+            }
+            p = p->next ;
+        }
+        pBigger->next = nullptr ;
+        pSmaller->next = headBigger.next ;
+        return headSmaller.next ;
+    }
+};