In 2017, I stepped down from my job as CTO of a 150-person software company to see if I could make money selling my own software on the Internet. Eight years later, I am now a full-time “solopreneur”—running a portfolio of revenue-generating software products as a full-time job. I now set my own…

If you need a file-like object that stores bytes in memory in Python, chances are you you’re using Pytho’s built-in io.BytesIO(). And since you’re already using an in-memory object, if your data is big enough you probably should try to save memory when reading that data back out. After all, it’s…

Building resilient distributed applications remains a tough challenge. It should be possible to focus almost entirely on the business logic and the complexity inherent to the domain. Instead, you need to review line-by-line and check: “what if the service crashes here?”, “what if the API we call…

Sharing is easy—and it helps more than you know. Prison cells around the world vary dramatically, reflecting each country’s approach to incarceration. Some facilities prioritize rehabilitation with comfortable living spaces, access to education, and even art programs, while others are stark,…

As we streak through winter, shorter daylight hours offer the best opportunity to view the dark skies before the clocks spring forward in March and the constellations shift again. This month is viewed as galaxy season in the northern hemisphere, offering the chance to see the Andromeda galaxy, our…

What It Means To presage something is to give or be a sign that it will happen in the future. Presage is a formal synonym of foreshadow, foretell, and predict. // The sudden gloom and ominous dark clouds clearly presaged a nasty storm. See the entry > presage in Context “What we’re really looking…

Given an array of numbers, you are required to calculate the mean (average) using recursion. Note: The mean of an array is the sum of its elements divided by the number of elements in the array. Examples: Input: 1 2 3 4 5 Output: 3 Explanation: The sum of elements (15) divided by the number of…

Given an algebraic expression as a string s containing operands (letters), + and - operators, and parentheses, simplify the expression by removing all parentheses and correctly applying the operators. Return the simplified expression without parentheses. Examples: Input:"(a - (b + c) + d)" Output:…

Given a binary tree, print all the ancestors of a particular key existing in the tree without using recursion.Here we will be discussing the implementation for the above problem. Examples: Input : 1 / \ 2 7 / \ / \ 3 5 8 9 / \ / 4 6 10 Key = 6 Output : 5 2 1 Ancestors of 6 are 5, 2 and 1. The idea…

Given a balanced expression, find if it contains duplicate parenthesis or not. A set of parenthesis are duplicate if the same subexpression is surrounded by multiple parenthesis. Examples: Below expressions have duplicate parenthesis - ((a+b)+((c+d))) The subexpression "c+d" is surrounded by two…

Try it on GfG Practice Given a string of balanced expressions, find if it contains a redundant parenthesis or not. Print 'Yes' if redundant, else 'No'. What are Redundant Parentheses? A pair of parentheses is redundant if removing them does not change the expression. This happens in two cases: Extra…

Try it on GfG Practice Given a string str consisting of opening and closing parenthesis '(' and ')', the task is to find the length of the longest valid parenthesis substring. Examples: Input: str = "((()" Output: 2 Explanation: Longest Valid Parentheses Substring is "()". Input: str = ")()())"…

Given an array of n elements and q queries, for each query that has index i, find the next greater element and print its value. If there is no such greater element to its right then print -1. Examples: Input : arr[] = {3, 4, 2, 7, 5, 8, 10, 6} query indexes = {3, 6, 1} Output: 8 -1 7 Explanation :…

Given n elements and the task is to implement a stack which removes and returns the maximum frequency element on every pop operation. If there's a tie in the frequency then the topmost highest frequency element will be returned. Examples: Input: push(4) 8 push(6) 6 push(7) 7 push(6) 6 push(8); 4…

Try it on GfG Practice Given an array arr[], the task is to find the sum of the maximum elements of every possible non-empty sub-arrays of the given array arr[]. Examples: Input: arr[] = [1, 3, 2] Output: 15 Explanation: All possible non-empty subarrays of [1, 3, 2] are {1}, {3}, {2}, {1, 3}, {3, 2}…

Given a binary tree, the task is to find the postorder traversal of the tree without using recursion. Examples: Input: Output: 4 5 2 3 1 Explanation: Postorder traversal (Left->Right->Root) of the tree is 4 5 2 3 1. Input: Output: 10 7 1 6 10 6 5 8 Explanation: Postorder traversal…

Given an array arr[] of n distinct elements, where each element is between 1 and n (inclusive), determine if it is stack-sortable. Note: An array a[] is considered stack-sortable if it can be rearranged into a sorted array b[] using a temporary stack stk with the following operations: Remove the…

Reverse a Stack without using recursion and extra space. Even the functional Stack is not allowed. Examples: Input : 1->2->3->4 Output : 4->3->2->1 Input : 6->5->4 Output : 4->5->6 We have discussed a way of reversing a stack in the below post. Reverse a Stack using Recursion The above solution…

The Tower of Hanoi is a mathematical puzzle with three poles and stacked disks of different sizes. The goal is to move all disks from the source pole to the destination pole using an auxiliary pole, following two rules: Only one disk can be moved at a time.A larger disk cannot be placed on a smaller…

Try it on GfG Practice Given the array arr[] of heights of certain buildings that lie adjacent to each other, Sunlight starts falling from the left side of the buildings. If there is a building of a certain height, all the buildings to the right side of it having lesser heights cannot see the sun.…

Try it on GfG Practice Given an array arr[] of integers, the task is to find the Next Greater Element for each element of the array in order of their appearance in the array. Note: The Next Greater Element for an element x is the first greater element on the right side of x in the array. Elements…

Try it on GfG Practice Given an array of integers, find the nearest smaller number for every element such that the smaller element is on the left side. Examples: Input: arr = [1, 6, 2] Output: [-1, 1, 1,] Explanation: There is no number at the left of 1. Smaller number than 6 and 2 is 1. Input: arr…

Design a stack with the following operations. push(Stack s, x): Adds an item x to stack s pop(Stack s): Removes the top item from stack s merge(Stack s1, Stack s2): Merge contents of s2 into s1. Time Complexity of all above operations should be O(1). If we use array implementation of the stack, then…

Create a customized data structure such that it has functions :- GetLastElement(); RemoveLastElement(); AddElement() GetMin() All the functions should be of O(1) Question Source : amazon interview questions Approach : create a custom stack of type structure with two elements, (element, min_till_now)…

Try it on GfG Practice Given a postfix expression, the task is to evaluate the postfix expression. A Postfix expression is of the form "a b operator" ("a b +") i.e., a pair of operands is followed by an operator. Examples: Input: arr = ["2", "3", "1", "*", "+", "9", "-"] Output: -4 Explanation: If…

Try it on GfG Practice You are given a queue Q, and your task is to reverse the elements of the queue. You are only allowed to use the following standard queue operations: enqueue(x): Add an item x to the rear of the queue.dequeue(): Remove an item from the front of the queue.empty(): Check if the…

The stack organization is very effective in evaluating arithmetic expressions. Expressions are usually represented in what is known as Infix notation, in which each operator is written between two operands (i.e., A + B). With this notation, we must distinguish between ( A + B )*C and A + ( B * C )…

Given an infix expression consisting of operators (+, -, *, /, ^) and operands (lowercase characters), the task is to convert it to a prefix expression. Infix Expression: The expression of type a 'operator' b (a+b, where + is an operator) i.e., when the operator is between two operands. Prefix…

We are given a queue data structure, the task is to implement a stack using a single queue. Also Read: Stack using two queues The idea is to keep the newly inserted element always at the front of the queue, preserving the order of previous elements by appending the new element at the back and…

Try it on GfG Practice Write a program to convert an Infix expression to Postfix form. Infix expression: The expression of the form "a operator b" (a + b) i.e., when an operator is in-between every pair of operands. Postfix expression: The expression of the form "a b operator" (ab+) i.e., When every…

Try it on GfG Practice Postfix to infix conversion involves transforming expressions where operators follow their operands (postfix notation) into standard mathematical expressions with operators placed between operands (infix notation). This conversion improves readability and understanding. Infix…

Try it on GfG Practice Given a Prefix expression, convert it into a Postfix expression. Conversion of Prefix expression directly to Postfix without going through the process of converting them first to Infix and then to Postfix is much better in terms of computation and better understanding the…

Try it on GfG Practice Infix : An expression is called the Infix expression if the operator appears in between the operands in the expression. Simply of the form (operand1 operator operand2). Example : (A+B) * (C-D) Prefix : An expression is called the prefix expression if the operator appears in…

How to Implement stack using a priority queue(using min heap)? Asked In: Microsoft, Adobe. Solution: In the priority queue, we assign priority to the elements that are being pushed. A stack requires elements to be processed in the Last in First Out manner. The idea is to associate a count that…

Last Updated : DiscussComments Question 1 Predict output of following program C++ #include int fun(int n) { if (n == 4) return n; else return 2 * fun(n + 1); } int main() { std::cout << fun(2); return 0; } C #include int fun(int n) { if (n == 4) return n; else return 2*fun(n+1); } int main() {…

Assume the structure of a Linked List node is as follows. C++ struct Node { int data; struct Node *next; }; // This code is contributed by SHUBHAMSINGH10 C struct Node { int data; struct Node *next; }; Java static class Node { int data; Node next; }; // This code is contributed by shubhamsingh10…

Question 1 Predict the output of the following program. What does the following fun() do in general? C++ #include using namespace std; int fun(int n, int* fp) { int t, f; if (n <= 2) { *fp = 1; return 1; } t = fun(n - 1, fp); f = t + *fp; *fp = t; return f; } int main() { int x = 15; cout << fun(5,…

Question 1 Consider the following recursive C function. Let len be the length of the string s and num be the number of characters printed on the screen. Give the relation between num and len where len is always greater than 0. C++ void abc(char *s) { if(s[0] == '\0') return; abc(s + 1); abc(s + 1);…