sovle problem Convert Sorted List To Binary Search Tree

Author: P-ppc

README.md

@@ -20,6 +20,7 @@ All solutions will be accepted!
 |226|[Invert Binary Tree](https://leetcode-cn.com/problems/invert-binary-tree/description/)|[java/py/js](./algorithms/InvertBinaryTree)|Easy|
 |693|[Binary Number With Alternating Bits](https://leetcode-cn.com/problems/binary-number-with-alternating-bits/description/)|[java/py/js](./algorithms/BinaryNumberWithAlternatingBits)|Easy|
 |108|[Convert Sorted Array To Binary Search Tree](https://leetcode-cn.com/problems/convert-sorted-array-to-binary-search-tree/description/)|[java/py/js](./algorithms/ConvertSortedArrayToBinarySearchTree)|Easy|
+|109|[Convert Sorted List To Binary Search Tree](https://leetcode-cn.com/problems/convert-sorted-list-to-binary-search-tree/description/)|[java/py/js](./algorithms/ConvertSortedListToBinarySearchTree)|Medium|
 |561|[Array Partition I](https://leetcode-cn.com/problems/array-partition-i/description/)|[java/py/js](./algorithms/ArrayPartitionI)|Easy|
 |463|[Island Perimeter](https://leetcode-cn.com/problems/island-perimeter/description/)|[java/py/js](./algorithms/IslandPerimeter)|Easy|
 |821|[Shortest Distance To A Character](https://leetcode-cn.com/problems/shortest-distance-to-a-character/description/)|[java/py/js](./algorithms/ShortestDistanceToACharacter)|Easy|

algorithms/ConvertSortedListToBinarySearchTree/README.md

@@ -0,0 +1,2 @@
+# Convert Sorted List To Binary Search Tree
+We can solve this problem by recursive, like [Convert Sorted Array To Binary Search Tree](./ConvertSortedArrayToBinarySearchTree)

algorithms/ConvertSortedListToBinarySearchTree/Solution.java

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+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode(int x) { val = x; }
+ * }
+ */
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode(int x) { val = x; }
+ * }
+ */
+class Solution {
+    public TreeNode sortedListToBST(ListNode head) {
+        int length = 0;
+        ListNode p = head;
+        
+        while (p != null) {
+            p = p.next;
+            length++;
+        }
+        return help(head, length);
+    }
+    
+    public TreeNode help(ListNode head, int length) {
+        if (length == 0) return null;
+        
+        ListNode p = head;
+        int mid = length / 2;
+        
+        for (int i = 0; i < mid; i++) p = p.next;
+        
+        TreeNode root = new TreeNode(p.val);
+        root.left = help(head, mid);
+        root.right = help(p.next, length - mid - 1);
+        return root;
+    }
+}

algorithms/ConvertSortedListToBinarySearchTree/solution.js

@@ -0,0 +1,43 @@
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val) {
+ *     this.val = val;
+ *     this.next = null;
+ * }
+ */
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val) {
+ *     this.val = val;
+ *     this.left = this.right = null;
+ * }
+ */
+/**
+ * @param {ListNode} head
+ * @return {TreeNode}
+ */
+var sortedListToBST = function(head) {
+    let length = 0,
+        p = head
+    
+    while (p) {
+        p = p.next
+        length++
+    }
+
+    return help(head, length)
+};
+
+var help = function (head, length) {
+    if (length == 0) return null
+        
+    let p = head,
+        mid = parseInt(length / 2)
+    
+    for (let i = 0; i < mid; i++) p = p.next
+
+    let root = new TreeNode(p.val)
+    root.left = help(head, mid)
+    root.right = help(p.next, length - mid - 1)
+    return root    
+};

algorithms/ConvertSortedListToBinarySearchTree/solution.py

@@ -0,0 +1,40 @@
+# Definition for singly-linked list.
+# class ListNode(object):
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+
+# Definition for a binary tree node.
+# class TreeNode(object):
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+class Solution(object):
+    def sortedListToBST(self, head):
+        """
+        :type head: ListNode
+        :rtype: TreeNode
+        """
+        length = 0
+        p = head
+        while p:
+            p = p.next
+            length += 1
+        
+        return self.help(head, length)
+    
+    def help(self, head, length):
+        if length == 0: return None
+        
+        p = head
+        mid = length / 2
+        
+        for i in xrange(mid):
+            p = p.next
+        
+        root = TreeNode(p.val)
+        root.left = self.help(head, mid)
+        root.right = self.help(p.next, length - mid - 1)
+        return root