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