2019-06-27

Author: JiayangWu

0143.重排链表/0143-重排链表.py

@@ -0,0 +1,49 @@
+# Definition for singly-linked list.
+# class ListNode(object):
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+
+class Solution(object):
+    def reorderList(self, head):
+        """
+        :type head: ListNode
+        :rtype: None Do not return anything, modify head in-place instead.
+        """
+        if not head or not head.next:
+            return head
+        
+        slow, fast = head, head
+        while fast and fast.next:
+            slow = slow.next
+            fast = fast.next.next
+        
+        l1, l2 = head, self.reverseList(slow.next)
+        slow.next = None
+        # self.printList(l1)
+        # self.printList(l2)
+        while l1 and l2:
+            cur = l2
+            l2 = l2.next
+
+            cur.next = l1.next
+            l1.next = cur
+            l1 = l1.next.next
+
+        return head
+    
+    def reverseList(self, head):
+        if not head or not head.next:
+            return head
+        p = self.reverseList(head.next)
+        head.next.next = head
+        head.next = None
+        return p
+    
+    def printList(self, head):
+        l = []
+        p = head
+        while p:
+            l.append(p.val)
+            p = p.next
+        print l

0147.对链表进行插入排序/0147-对链表进行插入排序.py

@@ -0,0 +1,34 @@
+# Definition for singly-linked list.
+# class ListNode(object):
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+
+class Solution(object):
+    def insertionSortList(self, head):
+        """
+        :type head: ListNode
+        :rtype: ListNode
+        """
+        if not head or not head.next:
+            return head
+        
+        dummy = ListNode(-1)
+        dummy.next = head
+        pre = head #pre始终指着排序好链表的最后一个节点
+        cur = head.next #cur始终指着未排序链表的第一个节点
+        while cur:
+            tail = cur.next
+            pre.next = tail  #把cur这个节点拿出来
+            
+            p = dummy
+            while p.next and p.next.val < cur.val: #找到插入的位置
+                p = p.next
+                
+            cur.next = p.next #把cur插入到p和p.next之间
+            p.next = cur
+            cur = tail
+            
+            if p == pre:#如果刚插入到了已排序链表的末尾
+                pre = pre.next #那么就更新pre
+        return dummy.next

0148.排序链表/0148-排序链表.py

@@ -0,0 +1,42 @@
+# Definition for singly-linked list.
+# class ListNode(object):
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+
+class Solution(object):
+    def sortList(self, head):
+        """
+        :type head: ListNode
+        :rtype: ListNode
+        """
+
+        if not head or not head.next:
+            return head
+        pre, slow, fast = head, head, head
+        while fast and fast.next:
+            pre = slow
+            slow = slow.next
+            fast = fast.next.next
+
+        pre.next = None
+        left, right = self.sortList(head), self.sortList(slow)
+        return self.merge(left, right)
+    
+    def merge(self, l1, l2):
+        if not l1:
+            return l2
+        if not l2:
+            return l1
+        
+        if l1.val < l2.val:
+            head = ListNode(l1.val)
+            head.next = self.merge(l1.next, l2)
+        else:
+            head = ListNode(l2.val)
+            head.next = self.merge(l1, l2.next)
+        return head
+            
+                
+            
+        

0156.上下翻转二叉树/0156-上下翻转二叉树.py

@@ -0,0 +1,31 @@
+# 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 upsideDownBinaryTree(self, root):
+        """
+        :type root: TreeNode
+        :rtype: TreeNode
+        """
+        #每一个节点变成其左孩子的右节点        
+        if not root or (not root.left and not root.right):
+            return root
+
+        parent, sibling = None, None
+        while root:
+            tmp = root.left
+            root.left = sibling
+            
+            sibling = root.right
+            root.right = parent
+            
+            parent = root
+            root = tmp
+            
+        return parent
+            
+            

0157.用Read4读取N个字符/0157-用Read4读取N个字符.py

@@ -0,0 +1,36 @@
+"""
+The read4 API is already defined for you.
+
+    @param buf, a list of characters
+    @return an integer
+    def read4(buf):
+
+# Below is an example of how the read4 API can be called.
+file = File("abcdefghijk") # File is "abcdefghijk", initially file pointer (fp) points to 'a'
+buf = [' '] * 4 # Create buffer with enough space to store characters
+read4(buf) # read4 returns 4. Now buf = ['a','b','c','d'], fp points to 'e'
+read4(buf) # read4 returns 4. Now buf = ['e','f','g','h'], fp points to 'i'
+read4(buf) # read4 returns 3. Now buf = ['i','j','k',...], fp points to end of file
+"""
+class Solution(object):
+    def read(self, buf, n):
+        """
+        :type buf: Destination buffer (List[str])
+        :type n: Number of characters to read (int)
+        :rtype: The number of actual characters read (int)
+        """
+        tmp = ["","","",""]
+        cnt = 0
+        read4(tmp)
+        while tmp != ["","","",""]:            
+            for i in range(4):
+                if tmp[i]:                    
+                    buf[cnt] = tmp[i]
+                    cnt += 1
+                    if cnt == n + 1:
+                        return n
+            tmp = ["","","",""]
+            read4(tmp)
+        return cnt
+            
+        

0190.颠倒二进制位/0190-颠倒二进制位.py

@@ -0,0 +1,10 @@
+class Solution:
+    # @param n, an integer
+    # @return an integer
+    def reverseBits(self, n):
+        b = bin(n)[2:]
+        b = "0" * (32 - len(b)) + b
+        # print b
+        # print b[::-1]
+        return int(b[::-1], 2)
+