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Page 1559 of 2109
How can I subtract a day from a Python date?
Introduction It is essential to have a module that can modify date and time since, as we all know, they are utilized in applications where we must keep track of date and time. A DateTime module in Python deals with dates and times (Python Date/Time Tutorial). Python comes with a built-in datetime module. Installation of two new libraries is necessary before any data modification may take place. Dates and timings are quickly retrieved using the arrow library. A DataFrame may be accessed and used thanks to the Pandas library. Go to an IDE console to install these libraries. ...
Read MoreCheck if the Left View of the given tree is sorted or not
In this problem, we will check whether the left view of the binary tree is sorted. The left view of the binary tree means nodes we can see when we look at the binary tree from the left side. In simple terms, we can see only the first node of each level. So, we need to extract the value of the first node and check whether they are sorted to get the output. Problem Statement We have given a binary tree. We need to print whether the binary tree's left view is sorted. If it is sorted, print 'Yes'. ...
Read MorePermutations and Combinations (Concept, Examples, C++ Program)
Permutations and Combinations refer to the arrangements of objects in mathematics. Permutation − In permutation, the order matters. Hence, the arrangement of the objects in a particular order is called a permutation. Permutations are of two types − Permutation with repetition Suppose we have to make a three-digit code. Some possible numbers are 123, 897, 557, 333, 000, and 001. So how many numbers can we make like this? Let us look at it this way− In the once place, we have ten options − 0-9 Similarly, at the tenth and the hundredth place also, we have ten options. 0-9. ...
Read MoreHCF of an array of fractions (or rational numbers)
HCF or the Highest common factor of two or more numbers refers to the highest number which divides them. A rational number is the quotient p/q of two numbers such that q is not equal to 0. Problem Statement Given an array with fractional numbers, find the HCF of the numbers. Example 1 Input [{4, 5}, {10, 12}, {24, 16}, {22, 13}] Output {2, 3120} Explanation The fractional numbers given are: 4/5, 10/12, 24/16 and 22/13 2/3120 is the largest number that divides all of them. Example 2 Input [{18, 20}, {15, 12}, {27, 12}, {20, 6}] ...
Read MoreStella Octangula Number
In mathematics, a Stella Octangula number is a figurate number based on the Stella Octangula, of the form n(2n2 − 1). Stella Octangula numbers which are perfect squares are 1 and 9653449. Problem Statement Given a number n, check whether it is the Stella Octangula number or not. The sequence of Stella Octangula numbers is 0, 1, 14, 51, 124, 245, 426, 679, 1016, 1449, 1990 Example1 Input x = 14 Output Yes Explanation $$\mathrm{For\: n = 2, expression \:n\lgroup 2n^2 – 1\rgroup is\: 14}$$ Example2 Input n = 22 Output No Explanation $$\mathrm{There \:is\: no\: ...
Read MoreNicomachus’ Theorem
According to Nicomachus’ Theorem, the sum of the cubes of the first n integers is equal to the square of the nth triangular number. Or, we can also say − The sum of cubes of first n natural numbers is equal to square of sum of first natural numbers. Putting it algebraically, $$\mathrm{\displaystyle\sum\limits_{i=0}^n i^3=\lgroup \frac{n^2+n}{2}\rgroup^2}$$ Theorem $$1^3 = 1$$ $$2^3 = 3 + 5$$ $$3^3 = 7 + 9 + 11$$ $$4^3 = 13 + 15 + 17 + 19\vdots$$ Generalizing $$n^3 =\lgroup n^2−n+1\rgroup+\lgroup n^2−n+3\rgroup+⋯+\lgroup n^2+n−1\rgroup$$ Proof By Induction For all n Ε Natural ...
Read MoreEqual sum array partition excluding a given element
Problem Statement For an index and an arr[]. Check if the array[] can be partitioned into two disjoint sets, excluding arr[index] such that the sum of both sets has equal value. Example 1 Input arr[] = {4, 3, 1, 2}, Index = 1 Output No Explanation We have to exclude arr[1] = 3 All possible sets are − Set 1: (4), Set 2: (2, 1), sum = 4≠3 Set 1: (4, 1), Set 2: (2), sum = 5≠2 Set 1: (4, 2), Set 2: (1), sum = 6≠1 No combination satisfies the conditions. Example 2Input arr[] ...
Read MoreSquared Triangular Number (Sum of Cubes)
A square triangular number, also referred to as a triangular square number, is a number that is both a triangular number and a perfect square. Square triangular numbers have an unlimited number of possible values; the first few are − 0, 1, 36, 1225, 41616... A triangular number or triangle number counts objects arranged in an equilateral triangle. The nth triangular number is the number of dots in the triangular arrangement with n dots on each side and is equal to the sum of the n natural numbers from 1 to n. The sequence of triangular numbers, ...
Read MoreAppend data to an empty Pandas DataFrame
Introduction A data structure known as a data frame is a two-dimensional labelled array with columns that might be of various data kinds. You can compare it to a spreadsheet, a SQL table, or even a dict of Series objects to better understand it. It is the panda item that is used the vast majority of the time. In addition to the data itself, you have the option of also passing parameters for the index (row labels) and columns (column labels). If you supply an index and/or columns, you are assuring that those elements will be present in the DataFrame ...
Read MoreFinding the k smallest values of a NumPy array
Finding the k smallest values of a NumPy arra Installation and Syntax Pip, Python's package installer, is often used to install NumPy. pip install numpy The following function may be used to identify the k NumPy array elements with the smallest values − np.sort(array)[:k] This returns the first k items of the sorted array after sorting it in ascending order. The array may be be sorted using the alternative syntax shown below, which will retrieve the last k entries and sort the array in descending order − np.sort(array)[::-1][:k] Algorithm The algorithm for finding the k smallest ...
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