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All posts tagged algorithms

Calculate the number of ways of representing n cents

Problem Statement Given an infinite number of quarters (25 cents), dimes (10 cents), nickels (5 cents) and pennies (1 cent), write code to calculate the number of ways of representing n cents Solution This is a recursive problem, so let’s figure out how to do makeChange(n) using prior solutions (i . . . Read more

Implement an algorithm to print all valid (e g , properly opened and closed) combinations of n-pairs of parentheses

Problem Statement Implement an algorithm to print all valid (e g , properly opened and closed) combinations of n-pairs of parentheses Example Input: 3 (e g , 3 pairs of parentheses) Output: ()()(), ()(()), (())(), ((())) Solution

Write a method to set all bits between i and j in N equal to M

Problem statement You are given two 32-bit numbers, and , and two bit positions, and . Write a method to set all bits between and in equal to (e g , becomes a substring of located at and starting at ) Example Input: , , , Output: Solution

Find the second smallest integer in array

Problem statement Given an array of integers, find the second smallest integer in that array. Solution

Count ways to reach the n stair

Problem statement There are stairs, a person standing at the bottom wants to reach the top. The person can climb either stair or stairs at a time. Count the number of ways, the person can reach the top. Solution We can solve this problem recursively. If the person were to . . . Read more

Divide two integers

Problem statement Divide two integers without using multiplication, division and mod operator. If it is overflow, return MAX_INT. Solution Obviously the naive approach to this problem would be to subtract the divisor from the dividend until the dividend becomes less than the divisor, while keeping track of how many times . . . Read more

Permutations II

Problem statement Given a list, nums, of distinct numbers, return all possible unique permutations. Sample input

Sample output

Solution In another post we showed how this problem can be solved iteratively. We can use the same technique but add a check to skip adding the number n to . . . Read more