Modular Arithmetic

Everything about Modular Arithmetic

1. Article · Data Structures and Algorithms (DSA)

   Subsets with MEX in Range

   Learn how to count array subsets whose MEX falls within a given range using frequencies, powers of two, and modular arithmetic in Java.

   Sandhiya PriyaOct 302,1501,000
2. Article · Data Structures and Algorithms (DSA)

   Count Palindromic Strings with Constraints

   Learn how to count palindromic strings of length up to n using the first k lowercase English letters, where no character appears more than twice. This article explains the key palindrome observations, separates even and odd-length cases, derives the permutation formulas, and provides an efficient Java solution using modular arithmetic. The solution achieves O(k) time complexity and O(1) auxiliary space.

   Sandhiya PriyaSep 22,4721,000
3. Article · Data Structures and Algorithms (DSA)

   Count Subsequences Divisible by N Using Dynamic Programming in Java

   Count Subsequences Divisible by N is a Dynamic Programming problem where we need to count the number of non-empty subsequences of a numeric string whose numeric value is divisible by a given integer n. The solution uses remainder-based DP to efficiently track subsequences for each possible remainder instead of generating all subsequences. The approach runs in O(|s| × n) time and O(n) space and handles large inputs efficiently.

   Sandhiya PriyaSep 24,2491,000
4. Article · Java

   Last Digit of a^b for Very Large Numbers

   Find the last digit of a^b for huge numbers. Learn about cyclicity of last digits and efficient modulo operations for large exponents.

   Sandhiya PriyaJun 22381
5. Article · Data Structures and Algorithms (DSA)

   Josephus Problem – Understanding the Famous Recurrence

   Master the Josephus Problem! Learn the elegant recurrence relation, its 0-based and 1-based solutions, and why iterative is superior.

   Sandhiya PriyaJun 108301,000