diff --git a/math/factorial_memoization.cpp b/math/factorial_memoization.cpp new file mode 100644 index 0000000000..c53df6e498 --- /dev/null +++ b/math/factorial_memoization.cpp @@ -0,0 +1,73 @@ +/** + * @file + * @brief [Factorial](https://en.wikipedia.org/wiki/Factorial) calculation using recursion and [memoization](https://en.wikipedia.org/wiki/Memoization) + * @details + * This program computes the factorial of a non-negative integer using recursion + * with memoization (top-down dynamic programming). It stores intermediate results + * to avoid redundant calculations for improved efficiency. + * + * Memoization is a form of caching where the result to an expensive function call + * is stored and returned. + * Example: + * Input: n = 5 + * Output: 120 + * + * Explanation: 5! = 5 × 4 × 3 × 2 × 1 = 120 + * + * The program uses a recursive function fact_recursion which caches computed + * results in a memo array to avoid recalculating factorials for the same numbers. + * + * Time Complexity: O(n) + * Space Complexity: O(n) + * @author [Vedant Mukhedkar](https://github.com/git5v) + */ + +#include // for std::cout +#include // For test cases +#include // For std::array +#include // For uint64_t + +/// Array to store computed factorials for memoization +std::array memo{0}; + +/** + * @namespace math + * @brief Math algorithms + */ +namespace math { + +/** + * @brief Computes the factorial of a non-negative integer using recursion and memoization. + * @param n The integer whose factorial is to be computed + * @returns The factorial of n + */ +uint64_t fact_recursion(uint64_t n) { + if (n == 0) return 1; // Base case: 0! = 1 + if (memo[n] != 0) return memo[n]; // Return already computed value + memo[n] = n * fact_recursion(n - 1); // Store and return the computed value + return memo[n]; +} + +} // namespace math +/** + * @brief Self-test implementations for the fact_recursion function. + * @returns void + */ +void test_fact_recursion() { + // Test cases for factorial computation + assert(math::fact_recursion(0) == 1); + assert(math::fact_recursion(1) == 1); + assert(math::fact_recursion(5) == 120); + assert(math::fact_recursion(10) == 3628800); + std::cout << "All test cases passed!\n"; +} + +/** + * @brief Main function to run test cases and interact with the user. + * @returns 0 on program success + */ +int main() { + // Run test cases + test_fact_recursion(); + return 0; +}