15 三数之和
给定一个包含 n 个整数的数组 nums，判断 nums 中是否存在三个元素 a，b，c ，使得 a + b + c = 0 ？找出所有满足条件且不重复的三元组。
注意：答案中不可以包含重复的三元组。
例如, 给定数组 nums = [-1, 0, 1, 2, -1, -4]， 满足要求的三元组集合为： [ [-1, 0, 1], [-1, -1, 2] ]
class Solution(object):
def threeSum(self, nums):
"""
:type nums: List[int]
:rtype: List[List[int]]
"""
nums.sort()
ans = []
for i in range(len(nums) - 2):
if i == 0 or nums[i] > nums[i-1]:
left = i + 1
right = len(nums) - 1
while left < right:
temp = nums[i] + nums[left] + nums[right]
if temp == 0:
ans.append([nums[i], nums[left], nums[right]])
left += 1
right -= 1
while left < right and nums[left] == nums[left -1]:
left += 1
while left < right and nums[right] == nums[right + 1]:
right -= 1
elif temp < 0 :
left += 1
else:
right -= 1
return ans
73. 矩阵置零
给定一个 m x n 的矩阵，如果一个元素为 0，则将其所在行和列的所有元素都设为 0。请使用原地算法。
示例 1:
输入: [ [1,1,1], [1,0,1], [1,1,1] ] 输出: [ [1,0,1], [0,0,0], [1,0,1] ]
示例 2:
输入: [ [0,1,2,0], [3,4,5,2], [1,3,1,5] ] 输出: [ [0,0,0,0], [0,4,5,0], [0,3,1,0] ]
代码：
class Solution(object):
def setZeroes(self, matrix):
"""
:type matrix: List[List[int]]
:rtype: void Do not return anything, modify matrix in-place instead.
"""
# row = len(matrix)
# cloumn = len(matrix[0])
# if row == 0 and cloumn == 0:
# return
# hasZero = 0
# for i in range(row): ### 第 i 行
# if matrix[i][0] == 0: ### 第0行
# hasZero = 1
# for j in range(1, cloumn): #### 第 i 行的第 j 列
# if matrix[i][j] == 0:
# matrix[i][0] = 0
# matrix[0][j] = 0
# for i in range(row-1, -1, -1): #### 2, 1, 0
# for j in range(cloumn-1, 0, -1): #### 2, 1
# if matrix[i][0] == 0 or matrix[0][j] == 0:
# matrix[i][j] = 0
# if hasZero == 1:
# matrix[i][0] = 0
# return
if len(matrix) == 0:
return ;
row, col = 1, 1
for i in range(0, len(matrix)):
if matrix[i][0] == 0:
col = 0
for j in range(0, len(matrix[0])):
if matrix[0][j] == 0:
row = 0
for i in range(1, len(matrix)):
for j in range(1, len(matrix[0])):
if matrix[i][j] == 0:
matrix[i][0] = 0
matrix[0][j] = 0
for i in range(1, len(matrix)):
for j in range(1, len(matrix[0])):
if matrix[i][0] == 0 or matrix[0][j] == 0:
matrix[i][j] = 0
if col == 0:
for i in range(0, len(matrix)):
matrix[i][0] = 0
if row == 0:
for j in range(0, len(matrix[0])):
matrix[0][j] = 0