ML studying

[Problem] Given an array nums of n integers, return an array of all the unique quadruplets [nums[a], nums[b], nums[c], nums[d]] such that: 0 List[List[int]]: if len(nums) tmp: right -= 1 else: left += 1 ans.sort() result = [] if len(ans) > 0: result.append(ans[0]) for k in range(1, len(ans)): if ans[k] != result[-1]: result.append(ans[k]) return result Well.. I have to find better solution TT

[Problem] Given an integer array nums of length n and an integer target, find three integers in nums such that the sum is closest to target. Return the sum of the three integers. You may assume that each input would have exactly one solution. [Explanation] This problem's goal is to find the sum of three elements which is closest to target. To solve it, two pointer algorithm is used with fixed po..

[Problem] You are given an m x n integer array grid where grid[i][j] could be: 1 representing the starting square. There is exactly one starting square. 2 representing the ending square. There is exactly one ending square. 0 representing empty squares we can walk over. -1 representing obstacles that we cannot walk over. Return the number of 4-directional walks from the starting square to the end..

[Problem] You are given an m x n integer array grid. There is a robot initially located at the top-left corner (i.e., grid[0][0]). The robot tries to move to the bottom-right corner (i.e., grid[m - 1][n - 1]). The robot can only move either down or right at any point in time. An obstacle and space are marked as 1 or 0 respectively in grid. A path that the robot takes cannot include any square th..

[Problem] There is a robot on an m x n grid. The robot is initially located at the top-left corner (i.e., grid[0][0]). The robot tries to move to the bottom-right corner (i.e., grid[m - 1][n - 1]). The robot can only move either down or right at any point in time. Given the two integers m and n, return the number of possible unique paths that the robot can take to reach the bottom-right corner. ..

[Problem] Given two sorted arrays nums1 and nums2 of size m and n respectively, return the median of the two sorted arrays. The overall run time complexity should be O(log (m+n)). [Explanation] Well.. this problem can be solve simply if there isn't condition about time complexity... In this problem, to satisfy time complextiy, it need to use binary search. Because some functions and algorithm li..

1) crosstab - To make frequency tableimport pandas as pd df = pd.read_csv('iris.csv') pd.crosstab(df.loc[:10, 'Sepal.Width'], df.loc[:10, 'Petal.Width'])2) isna() isna() is the same with isnull() In reverse, notna() is the same with notnull() 3) fillna() To handle nan value easily, fillna() is used.Signature: df.fillna(value=None, method=None, axis=None, inplace=False, limit=None, downcast=None,..

[Problem] Given a string containing digits from 2-9 inclusive, return all possible letter combinations that the number could represent. Return the answer in any order. A mapping of digits to letters (just like on the telephone buttons) is given below. Note that 1 does not map to any letters. [Explanation] Given phone number, I have to find all combinations of string that is contained in each num..

[Problem] Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target. You may assume that each input would have exactly one solution, and you may not use the same element twice. You can return the answer in any order. [Explanation] There are given array and a target value. In the array, two values that can make the target value by add..

1) iloc vs loc iloc is to use integer index in dataframe. loc is to use category name in dataframe.import pandas as pd df = pd.read_csv('iris.csv') %To read csv file, use pandas.read_csv df.head(2)df_sub1 = df.loc[:, ['petal.length', 'petal.width', 'variety']] print(df_sub1.head(2)) df_sub2 = df.iloc[:, 2:] print(df_sub2.head(2)) 2) unique It is used to see what categories are included in specif..