Merge pull request algorithm001#29 from yuanyunxu/master

Temp solve two problem

Author: GeekUniversity

Week_01/id_122/LeetCode_142_122.py

@@ -0,0 +1,26 @@
+# Definition for singly-linked list.
+# class ListNode(object):
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+
+class Solution(object):
+    def detectCycle(self, head):
+        """
+        :type head: ListNode
+        :rtype: ListNode
+        """
+        if head is None or head.next is None or head.next.next is None:
+            return
+        p1 = head.next
+        p2 = head.next.next
+        while(p2 is not None and p2.next is not None and p2.next.next is not None):
+            p1 = p1.next
+            p2 = p2.next.next
+            if p1 is p2:
+                p1 = head
+                while p1 is not p2:
+                    p1 = p1.next
+                    p2 = p2.next
+                return p1
+        return 

Week_01/id_122/LeetCode_21_122.php

@@ -0,0 +1,75 @@
+<?php
+/**
+ * Created by PhpStorm.
+ * User: yuanyunxu
+ * Date: 19/4/16
+ * Time: ÏÂÎç3:41
+ */
+
+/**
+ * Definition for a singly-linked list.
+ * class ListNode {
+ *     public $val = 0;
+ *     public $next = null;
+ *     function __construct($val) { $this->val = $val; }
+ * }
+ */
+
+class ListNode {
+    public $val = 0;
+    public $next = null;
+    function __construct($val) { $this->val = $val; }
+}
+
+class Solution {
+
+    /**
+     * @param ListNode $l1
+     * @param ListNode $l2
+     * @return ListNode
+     */
+    function mergeTwoLists($l1, $l2) {
+        if ($l1 == null) {
+            return $l2;
+        }
+
+        if ($l2 == null) {
+            return $l1;
+        }
+
+        $first = $l1;
+        $second = $l2;
+
+        if ($first->val <= $second->val) {
+            $head = $first;
+            $first = $first->next;
+        } else {
+            $head = $second;
+            $second = $second->next;
+        }
+
+        $now = $head;
+
+        while (true) {
+            if ($first == null) {
+                $now->next = $second;
+                break;
+            }
+            if ($second == null) {
+                $now->next = $first;
+                break;
+            }
+
+            if ($first->val <= $second->val) {
+                $now->next = $first;
+                $first = $first->next;
+                $now = $now->next;
+                continue;
+            }
+            $now->next = $second;
+            $second = $second->next;
+            $now = $now->next;
+        }
+        return $head;
+    }
+}

Week_01/id_122/LeetCode_24_122.php

@@ -0,0 +1,49 @@
+<?php
+/**
+ * Definition for a singly-linked list.
+ * class ListNode {
+ *     public $val = 0;
+ *     public $next = null;
+ *     function __construct($val) { $this->val = $val; }
+ * }
+ */
+class ListNode {
+    public $val = 0;
+    public $next = null;
+    function __construct($val) { $this->val = $val; }
+}
+
+class Solution {
+
+    /**
+     * @param ListNode $head
+     * @return ListNode
+     */
+    function swapPairs($head) {
+
+        //没有元素，或者只有一个元素
+        if ($head == null || $head->next == null) {
+            return $head;
+        }
+        $shaoBing = new ListNode(null);
+        $shaoBing->next = $head->next;
+
+        //到这里至少链表中至少有两个元素
+        $prev = $head;
+        $prior = $prev->next;
+        $next = $prior->next;
+
+        while ($next && $next->next) {
+            $prev->next = $next->next;
+            $prior->next = $prev;
+            $prev = $next;
+            $prior = $next->next;
+            $next = $prior->next;
+        }
+
+        //最后交换末尾两个元素, 针对单数个链表元素做处理
+        $prev->next = $next ? $next : null;
+        $prior->next = $prev;
+        return $shaoBing->next;
+    }
+}

Week_01/id_122/LeetCode_83_122.php

@@ -0,0 +1,46 @@
+<?php
+/**
+ * Created by PhpStorm.
+ * User: yuanyunxu
+ * Date: 19/4/16
+ * Time: ÏÂÎç3:15
+ */
+
+/**
+ * Definition for a singly-linked list.
+ * class ListNode {
+ *     public $val = 0;
+ *     public $next = null;
+ *     function __construct($val) { $this->val = $val; }
+ * }
+ */
+
+class ListNode {
+     public $val = 0;
+     public $next = null;
+     function __construct($val) { $this->val = $val; }
+}
+
+class Solution {
+
+    /**
+     * @param ListNode $head
+     * @return ListNode
+     */
+    function deleteDuplicates($head) {
+        if ($head == null) {
+            return $head;
+        }
+        $prior = $head;
+        while ($prior->next) {
+            $next = $prior->next;
+            if ($prior->val == $next->val) {
+                $prior->next = $next->next;
+                $next->next = null;
+                continue;
+            }
+            $prior = $prior->next;
+        }
+        return $head;
+    }
+}