add some code

Author: huxiaoman7

python/19_RemoveNthNodeFromEndofList.py

@@ -5,3 +5,32 @@
 # @File    : 19_RemoveNthNodeFromEndofList.py
 # @Package : LeetCode
 # @E-mail  : charlotte77_hu@sina.com
+
+# Definition for singly-linked list.
+# class ListNode(object):
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+
+class Solution(object):
+    def removeNthFromEnd(self, head, n):
+        """
+        :type head: ListNode
+        :type n: int
+        :rtype: ListNode
+        """
+        new_head = ListNode(0)
+        new_head.next =head
+        fast=slow=new_head
+        for i in range(n+1):
+            fast = fast.next
+        while fast:
+            fast=fast.next
+            slow=slow.next
+        slow.next=slow.next.next
+        return new_head.next
+
+
+if __name__=='__main__':
+    s = Solution()
+    print  s.removeNthFromEnd([1,2,3,4,5],2)

python/20_validParentheses.py

@@ -5,3 +5,24 @@
 # @File    : 20_validParentheses.py
 # @Package : LeetCode
 # @E-mail  : charlotte77_hu@sina.com
+
+class Solution(object):
+    def isValid(self, s):
+        """
+        :type s: str
+        :rtype: bool
+        """
+        pars = [None]
+        #这个字典建立的顺序也很重要
+        parmap = {')':'(','}':'{',']':'['}
+        for c in s:
+            if c in parmap:
+                if parmap[c] !=pars.pop():
+                    return False
+            else:
+                pars.append(c)
+        return len(pars) == 1
+
+if __name__=='__main__':
+    s = Solution()
+    print s.isValid(")(")

python/21_MergeTwoSortedLists.py

@@ -5,3 +5,30 @@
 # @File    : 21_MergeTwoSortedLists.py
 # @Package : LeetCode
 # @E-mail  : charlotte77_hu@sina.com
+
+# Definition for singly-linked list.
+# class ListNode(object):
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+
+class Solution(object):
+    def mergeTwoLists(self, l1, l2):
+        """
+        :type l1: ListNode
+        :type l2: ListNode
+        :rtype: ListNode
+        """
+        if not l1 or not l2:
+            return l1 or l2
+        head = cur = ListNode(0)
+        while l1 and l2:
+            if l1.val <l2.val:
+                cur.next = l1
+                l1 = l1.next
+            else:
+                cur.next = l2
+                l2 = l2.next
+            cur = cur.next
+        cur.next = l1 or l2
+        return head.next

python/22_GenerateParentheses.py

@@ -5,3 +5,22 @@
 # @File    : 22_GenerateParentheses.py
 # @Package : LeetCode
 # @E-mail  : charlotte77_hu@sina.com
+
+
+class Solution(object):
+    def generateParenthesis(self, n):
+        """
+        :type n: int
+        :rtype: List[str]
+        """
+        def generate(p,left,right):
+            if right >= left >=0:
+                if not right:
+                    yield p
+                for q in generate(p+'(' ,left-1,right):yield q
+                for q in generate(p+')',left,right -1):yield q
+        return list(generate('',n,n))
+
+if __name__ == "__main__":
+    s = Solution()
+    print s.generateParenthesis(3)

python/23_MergeKSortedLists.py

@@ -5,3 +5,19 @@
 # @File    : 23_MergeKSortedLists.py
 # @Package : LeetCode
 # @E-mail  : charlotte77_hu@sina.com
+
+
+from Queue import PriorityQueue
+
+class Solution(object):
+    def mergeKLists(self, lists):
+        dummy = ListNode(None)
+        curr = dummy
+        q = PriorityQueue()
+        for node in lists:
+            if node: q.put((node.val,node))
+        while q.qsize()>0:
+            curr.next = q.get()[1]
+            curr=curr.next
+            if curr.next: q.put((curr.next.val, curr.next))
+        return dummy.next

python/24_SwapNodesInPairs.py

@@ -5,3 +5,27 @@
 # @File    : 24_SwapNodesInPairs.py
 # @Package : LeetCode
 # @E-mail  : charlotte77_hu@sina.com
+
+# Definition for singly-linked list.
+# class ListNode(object):
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+
+class Solution(object):
+    def swapPairs(self, head):
+        """
+        :type head: ListNode
+        :rtype: ListNode
+        """
+        if not head or not head.next:
+            return head
+        pre = new_head = ListNode(0)
+        while head and head.next:
+            tmp = head.next
+            head.next = tmp.next
+            tmp.next = head
+            pre.next = tmp
+            pre = head
+            head = head.next
+        return new_head.next

python/25_ReverseNodesinK-Group.py

@@ -5,3 +5,32 @@
 # @File    : 25_ReverseNodesinK-Group.py
 # @Package : LeetCode
 # @E-mail  : charlotte77_hu@sina.com
+
+# Definition for singly-linked list.
+# class ListNode(object):
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+
+class Solution(object):
+    def reverseKGroup(self, head, k):
+        """
+        :type head: ListNode
+        :type k: int
+        :rtype: ListNode
+        """
+        dummy = jump = ListNode(0)
+        dummy.next = l = r = head
+
+        while True:
+            count = 0
+            while r and count < k:
+                r = r.next
+                count += 1
+            if count == k:
+                pre, cur = r, l
+                for _ in range(k):
+                    cur.next, cur, pre = pre, cur.next, cur
+                jump.next, jump, l = pre, l, r
+            else:
+                return dummy.next

python/26_RemoveDuplicatesfromSortedArray.py

@@ -5,3 +5,44 @@
 # @File    : 26_RemoveDuplicatesfromSortedArray.py
 # @Package : LeetCode
 # @E-mail  : charlotte77_hu@sina.com
+
+class Solution1(object):
+    def removeDuplicates(self, nums):
+        """
+        :type nums: List[int]
+        :rtype: int
+        """
+        # 方法一：用两个指针，一个指针用于扫描遍历整个列表，
+        # 另一个指针时终止向下一个数字要写入列表的位置，
+        # 效果相当于在便利列表的时候，将不同的数字重新写入到原数组
+
+        if len(nums)==0:
+            return 0
+        cur=0
+        for i in range(1,len(nums)):
+            if nums[i] != nums[cur]:
+                cur +=1
+                nums[cur] = nums[i]
+        return cur+1
+
+class Solution2(object):
+    def removeDuplicates(self, nums):
+        """
+        :type nums: List[int]
+        :rtype: int
+        """
+        # 方法二：用一个计数器记录当前有多少重复数字，
+        # 以此来决定下一个要写入数组的数字的位置，
+        # 以及当便利玩数组时得到的新长度
+        count = 0
+        for i in range(1,len(nums)):
+            if nums[i] == nums[i-1]:
+                count +=1
+            else:
+                nums[i-count] = nums[i]
+        return len(nums)-count
+
+
+if __name__=='__main__':
+    s = Solution2()
+    print s.removeDuplicates([1,1,2])

python/27_RemoveElement.py

@@ -5,3 +5,26 @@
 # @File    : 27_RemoveElement.py
 # @Package : LeetCode
 # @E-mail  : charlotte77_hu@sina.com
+
+
+class Solution(object):
+    def removeElement(self, nums, val):
+        """
+        :type nums: List[int]
+        :type val: int
+        :rtype: int
+        """
+        # 方法一：用两个指针，一个指针顺序扫描素有元素判断当前元素是否需要删除，另一个指针一直指向下一个不是要删除元素的位置
+        # 这样相当于把原数组中要删除的数去除后，所有其他数字前移
+
+        length = 0
+
+        for i in xrange(len(nums)):
+            if nums[i] !=val:
+                nums[length] =nums[i]
+                length += 1
+        return length
+
+if __name__=='__main__':
+    s = Solution()
+    print s.removeElement([2,3,3,2],3)

python/28_ImplementstrStr().py

@@ -5,3 +5,26 @@
 # @File    : 28_ImplementstrStr().py
 # @Package : LeetCode
 # @E-mail  : charlotte77_hu@sina.com
+
+
+class Solution(object):
+    def strStr(self, haystack, needle):
+        """
+        :type haystack: str
+        :type needle: str
+        :rtype: int
+        """
+        if not needle:
+            return 0
+        for i in xrange(len(haystack) - len(needle)+1):
+            if haystack[i] == needle[0]:
+                j = 1
+                while j  < len(needle)  and haystack[i+j] ==needle[j]:
+                    j+=1
+                if j ==len(needle):
+                    return i
+        return -1
+
+if __name__=='__main__':
+    s = Solution()
+    print s.strStr('hello','ll')