Programming Articles

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The k-th Lexicographical String of All Happy Strings of Length n in C++

Arnab Chakraborty
Arnab Chakraborty
Updated on 11-Mar-2026 304 Views

Suppose we have a string. We will call that a happy string when it consists of only ['a', 'b', 'c'] letters, and s[i] != s[i + 1] for all values of i from 1 to length of s - 1 (here the string is 1-indexed).So, if we have two integers n and k, consider a list of all happy strings of length n sorted in lexicographical order. We have to find the the kth string of this list or return an empty string if there are less than k happy strings of length nSo, if the input is like n ...

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How to extract columns of a data frame with their names after converting it to a time series object in R?

Nizamuddin Siddiqui
Nizamuddin Siddiqui
Updated on 11-Mar-2026 554 Views

To access columns of data frame in R, we just need to use $ sign but if the data frame is converted to a time series object then all the columns will behave as a time series, hence, we cannot simply use $ sign. For this purpose, we would need to use single square brackets and pass the appropriate column inside it. Look at the below examples to understand how it works.Example 1Consider the below data frame:> set.seed(147) > x1 x2 x3 df1 df1Outputx1 x2 x3 1 5 11 4 2 5 5 3 3 4 6 2 4 10 ...

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How to exclude extra margin between points and the axes for a plot created by using ggplot2 in R?

Nizamuddin Siddiqui
Nizamuddin Siddiqui
Updated on 11-Mar-2026 1K+ Views

In a plot created by using ggplot package there exists an extra area around all the sides of the plot which uses extra space, thus we might want to get rid of that space by removing that extra margin area. It can be done by setting the scale for both the axes to zero with the help of scale_x_continuous and scale_y_continuous function.Consider the below data frame −Exampleset.seed(151) x

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Display Table of Food Orders in a Restaurant in C++

Arnab Chakraborty
Arnab Chakraborty
Updated on 11-Mar-2026 447 Views

Suppose we have an array orders, which represents the orders that customers have done in a restaurant. So, orders[i]=[cust_namei, table_numi, food_itemi] where cust_namei is the customer name, table_numi is the customers table number, and food_itemi is the item customer orders.We have to return the restaurant's “display table”. Here the “display table” is a table whose row entries denote how many of each food item each table ordered. The first column will be the table number and the remaining columns correspond to each food item in alphabetical order. First row should be a header whose first column is “Table”, followed by ...

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Minimum Number of Frogs Croaking in C++

Arnab Chakraborty
Arnab Chakraborty
Updated on 11-Mar-2026 361 Views

Suppose we have a string called croakOfFrogs, this represents a combination of the string "croak" from different frogs, multiple frogs can croak at the same time, so multiple "croak" are mixed. We have to find the minimum number of different frogs to finish all the croak in the given string.Here a valid "croak" means a frog is generating 5 letters ‘c’, ’r’, ’o’, ’a’, ’k’ sequentially. The frogs have to generate all five letters to finish a croak. If the string is not a valid "croak" string then return -1.So, if the input is like "crcoakroak", then the output will ...

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Maximum Points You Can Obtain from Cards in C++

Arnab Chakraborty
Arnab Chakraborty
Updated on 11-Mar-2026 392 Views

Suppose there are several cards arranged in a row, each card has associated points, and these points are given in the integer array called cardPoints. In one step, we can take one card from the beginning or from the end of the row. We have to take exactly k cards. The final score will be the sum of the points of the cards we have taken. So, if we have integer array cardPoints and the integer k, then find the maximum score we can obtain.So, if the input is like cardPoints = [1, 2, 3, 4, 5, 6, 1], k ...

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Diagonal Traverse II in C++

Arnab Chakraborty
Arnab Chakraborty
Updated on 11-Mar-2026 237 Views

Suppose we have a list of lists called nums, we have to show all elements of nums in diagonal order.So, if the input is likethen the output will be [1, 6, 2, 8, 7, 3, 9, 4, 12, 10, 5, 13, 11, 14, 15, 16]To solve this, we will follow these steps −Define an array retDefine one 2D array vfor initialize i := 0, when i < size of nums, update (increase i by 1), do −for initialize j := 0, when j < size of nums[i], update (increase j by 1), do −insert { nums[i, j], i, j } ...

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Max Difference You Can Get From Changing an Integer in C++

Arnab Chakraborty
Arnab Chakraborty
Updated on 11-Mar-2026 286 Views

Suppose we have an integer num. We will apply the following steps exactly two times, the steps are like −Pick a digit x in range 0 to 9.Pick another digit y also in range 0 to 9. The digit y can be equal to x.Replace all the occurrences of x in the decimal representation of num by y. The new integer cannot have any leading zeros, also the new integer cannot be of value 0.Now consider a and b be the results of applying the operations to num the first and second times, respectively. Then find the max difference between ...

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How to split a data frame in R with conditional row values?

Nizamuddin Siddiqui
Nizamuddin Siddiqui
Updated on 11-Mar-2026 3K+ Views

The splitting of data frame is mainly done to compare different parts of that data frame but this splitting is based on some condition and this condition can be row values as well. For example, if we have a data frame df where a column represents categorical data then the splitting based on the categories can be done by using subset function as shown in the below examples.Example1Consider the below data frame:> Country Ratings df1 df1Output Country Ratings 1 India   1 2 China   2 3 Russia  5 4 Sudan   3 5 India   5 6 China   5 ...

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Check If a String Can Break Another String in C++

Arnab Chakraborty
Arnab Chakraborty
Updated on 11-Mar-2026 323 Views

Suppose we have two strings s1 and s2 whose size are same; we have to check whether some permutation of string s1 can break some permutation of string s2 or vice-versa. A string a can break string b if x[i] >= y[i] (in alphabetical order) for all i in range 0 to n-1.So, if the input is like s1 = abc and s2 = xya, then the output will be true. This is because "ayx" is a permutation of s2 that can break to string "abc" which is a permutation of s1="abc".To solve this, we will follow these steps −Define ...

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