zeroes

bit_manipulation/count_of_trailing_ciphers_in_factorial_n.cpp

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+/**
+ * @file
+ * @brief Program to count number of ciphers in `n!`(https://www.tutorialspoint.com/count-trailing-zeros-in-factorial-of-a-number-in-cplusplus).
+ * @details
+ * We are given a number. The algorithm finds all
+ * the zeroes at the end of factorial of that number.
+ * @author [Swastika Gupta](https://github.com/Swastyy)
+ */
+
+#include <cassert>   /// for assert
+#include <iostream>  /// for IO operations
+
+/**
+ * @namespace bit_manipulation
+ * @brief Bit manipulation algorithms
+ */
+namespace bit_manipulation {
+/**
+ * @namespace numberOfCiphersInFactorialN
+ * @brief Program to count number of ciphers in `n!`(https://www.tutorialspoint.com/count-trailing-zeros-in-factorial-of-a-number-in-cplusplus).
+ */
+namespace numberOfCiphersInFactorialN {
+ /**
+ * @brief Function to count the number of trailing ciphers.
+ * @param n, Number for which `n!` ciphers are returned
+ * @return count, Number of ciphers in `n!`.
+ */
+
+uint64_t numberOfCiphersInFactorialN(uint64_t n) {
+    // count is to store the number of 5's in factorial(n)
+    uint64_t count = 0;
+
+    // Keep dividing n by powers of
+    // 5 and update count
+    for (uint64_t i = 5; n / i >= 1; i *= 5) {
+        count += static_cast<uint64_t>(n) / i;
+    }
+
+    return count;
+}
+}  // namespace numberOfCiphersInFactorialN
+}  // namespace bit_manipulation
+
+/**
+ * @brief Test implementations
+ * @returns void
+ */
+static void test() {
+    // Test 1
+    std::cout << "1st test ";
+    assert(bit_manipulation::numberOfCiphersInFactorialN::numberOfCiphersInFactorialN(395) == 97);
+    std::cout << "passed" << std::endl;
+
+    // Test 2
+    std::cout << "2nd test ";
+    assert(bit_manipulation::numberOfCiphersInFactorialN::numberOfCiphersInFactorialN(977) == 242);
+    std::cout << "passed" << std::endl;
+
+    // Test 3
+    std::cout << "3rd test ";
+    assert(bit_manipulation::numberOfCiphersInFactorialN::numberOfCiphersInFactorialN(871) == 215);
+    std::cout << "passed" << std::endl;
+
+    // Test 4
+    std::cout << "4th test ";
+    assert(bit_manipulation::numberOfCiphersInFactorialN::numberOfCiphersInFactorialN(239) == 57);
+    std::cout << "passed" << std::endl;
+
+    // Test 5
+    std::cout << "5th test ";
+    assert(bit_manipulation::numberOfCiphersInFactorialN::numberOfCiphersInFactorialN(0) == 0);
+    std::cout << "passed" << std::endl;
+}
+
+/**
+ * @brief Main function
+ * @returns 0 on exit
+ */
+int main() {
+    test();  // run self-test implementations
+    return 0;
+}