Leetcode刷題記錄 劍指offer

面試題3：陣列中重複數字

# 使用set，時間複雜度o(n),空間複雜度o(n)

class
solution(object):
deffindrepeatnumber(self, nums):
""":type nums: list[int]
:rtype: int
"""a =set()
for num in
nums:
if num in
a:                
return
num            a.add(num)

#

桶思想，時間複雜度o(n),空間複雜度o(1)
class
solution(object):
deffindrepeatnumber(self, nums):
""":type nums: list[int]
:rtype: int
"""for i in
range(len(nums)):
val =nums[i]
if val != i and val ==nums[val]:
return
val            nums[i], nums[val] = nums[val], nums[i]

面試題4：二維陣列中的查詢

#

從右上往左下推
class
solution(object):
deffindnumberin2darray(self, matrix, target):
""":type matrix: list[list[int]]
:type target: int
:rtype: bool
"""if matrix ==  or matrix ==:
return
false
c = len(matrix[0])-1l =0
while
true:
if matrix[l][c] ==target:
return
true
if matrix[l][c] >target:
c -= 1
else
:                l += 1
if l > len(matrix)-1 or c <0:
return false

面試題5：替換空格

class

solution(object):
defreplacespace(self, s):
""":type s: str
:rtype: str
"""l = [''] *len(s)
for i in
range(len(s)):
if s[i] == '':
l[i] = '
%20'
else
:                l[i] =s[i]
return
''.join(l)

面試題6：從尾到頭列印鍊錶

#

非遞迴class
solution(object):
defreverseprint(self, head):
""":type head: listnode
:rtype: list[int]
"""result =
while
head:
head =head.next
return result[::-1]

#

遞迴class
solution(object):
defreverseprint(self, head):
""":type head: listnode
:rtype: list[int]
"""result =
defhelper(root):
ifnot
root:
return
helper(root.next)
helper(head)
return result

面試題7：重建二叉樹

class

solution(object):
defbuildtree(self, preorder, inorder):
""":type preorder: list[int]
:type inorder: list[int]
:rtype: treenode
"""def
helper(inc_start, inc_end):
if inc_start ==inc_end:
return
none
inc_value =preorder[self.pre_index]
root =treenode(inc_value)
self.pre_index += 1root.left =helper(inc_start, inc_value_map[inc_value])
root.right = helper(inc_value_map[inc_value] + 1, inc_end)
return
root
self.pre_index =0
inc_value_map = 
return helper(0, len(inorder))

面試題9：用兩個棧實現佇列

class

cqueue(object):
def__init__
(self):
self.l1 =
self.l2 =
def        
""":type value: int
:rtype: none
"""        
defdeletehead(self):
""":rtype: int
"""if
notself.l1:
ifnot
self.l2:
return -1
for i in
range(len(self.l2)):
return self.l1.pop()

面試題10-i：斐波那契數列

class

solution(object):
deffib(self, n):
""":type n: int
:rtype: int
"""if n ==0:
return
0         a =0
b = 1
while n != 1:
a, b = b, a+b
n -= 1
return b % 1000000007

面試題10-ii：青蛙跳台階問題

class

solution(object):
defnumways(self, n):
""":type n: int
:rtype: int
"""if n ==0:
return 1a = 1b = 1
while n != 1:
a, b = b, a+b
n -= 1
return b % 1000000007

劍指 offer 刷題記錄

任誰都躲不過找工作的問題，好希望能多準備一些時間，奈何時間不等人，每天刷幾道題，並且記錄下來吧 def replacespace s write code here num space 0 new s for i in range len s if i num space 1 for i in ra...

劍指offer刷題記錄

遞迴法 鍊錶的後續遍歷，並用self.k來記錄倒數節點的位置，找到了就返回找到的節點，否則返回none coding utf 8 class listnode def init self,x self.val x self.next none class solution def init self...

劍指offer刷題記錄 綜合

將乙個字串轉換成乙個整數，要求不能使用字串轉換整數的庫函式。數值為0或者字串不是乙個合法的數值則返回0 輸入描述 輸入乙個字串,包括數字字母符號,可以為空 輸出描述 如果是合法的數值表達則返回該數字，否則返回0 做這個題目做的真的很煩，最麻煩的就是判斷當前是否越界。可儲存的最大的正數末位為7，可儲存...