From 661ef7ab5eab041306cb86305a9ad771aa6787ad Mon Sep 17 00:00:00 2001
From: yashrajyash <yashrajyash18@gmail.com>
Date: Sat, 1 Jan 2022 11:48:04 +0530
Subject: [PATCH] Added count_bits_flip.cpp

---
 bit_manipulation/count_bits_flip.cpp | 88 ++++++++++++++++++++++++++++
 1 file changed, 88 insertions(+)
 create mode 100644 bit_manipulation/count_bits_flip.cpp

diff --git a/bit_manipulation/count_bits_flip.cpp b/bit_manipulation/count_bits_flip.cpp
new file mode 100644
index 000000000..4946677f4
--- /dev/null
+++ b/bit_manipulation/count_bits_flip.cpp
@@ -0,0 +1,88 @@
+/**
+ * @file
+ * @brief Implementation to
+ * [Count number of bits to be flipped to convert A to B]
+ * (https://www.geeksforgeeks.org/count-number-of-bits-to-be-flipped-to-convert-a-to-b/)
+ * in an integer.
+ *
+ * @details
+ * We are given two numbers A and B. Our task is to count the number of bits
+ * needed to be flipped to convert A to B.
+ *
+ * Explanation:
+ *
+ * A  = 01010 B  = 10100
+ * As we can see, the bits of A that need to be flipped are 01010.
+ * If we flipthese bits, we get 10100, which is B.
+ *
+ * Worst Case Time Complexity: O(log n)
+ * Space complexity: O(1)
+ * @author [Yash Raj Singh](https://github.com/yashrajyash)
+ */
+#include <cassert>   /// for assert
+#include <iostream>  /// for IO operations
+/**
+ * @namespace bit_manipulation
+ * @brief Bit manipulation algorithms
+ */
+namespace bit_manipulation {
+/**
+ * @namespace count_bits_flip
+ * @brief Functions for the [count bits
+ * flip](https://www.geeksforgeeks.org/count-set-bits-in-an-integer/)
+ * implementation
+ */
+namespace count_bits_flip {
+/**
+ * @brief The main function implements count of bits flip required
+ * @param A is the given number whose bits will be flipped to get number B
+ * @param B is the given target number
+ * @returns total number of bits needed to be flipped to convert A to B
+ */
+std::uint64_t countBitsFlip(
+    std ::int64_t A,
+    std ::int64_t B) {  // int64_t is preferred over int so that
+                        // no Overflow can be there.
+
+    int count =
+        0;  // "count" variable is used to count number of bits flip of the
+            // number A to form B in binary representation of number 'n'
+    A = A ^ B;
+    while (A) {
+        A = A & (A - 1);
+        count++;
+    }
+    return count;
+}
+}  // namespace count_bits_flip
+}  // namespace bit_manipulation
+
+/**
+ * @brief Self-test implementations
+ * @returns void
+ */
+static void test() {
+    // A = 10, B = 20 return 4
+    assert(bit_manipulation::count_bits_flip::countBitsFlip(10, 20) == 4);
+    // A = 20, B = 25 return 3
+    assert(bit_manipulation::count_bits_flip::countBitsFlip(20, 25) == 3);
+    // A = 7, B = 10 return 3
+    assert(bit_manipulation::count_bits_flip::countBitsFlip(7, 10) == 3);
+    // A = 17, B = 25 return 1
+    assert(bit_manipulation::count_bits_flip::countBitsFlip(17, 25) == 1);
+    // A = 11, B = 8 return 2
+    assert(bit_manipulation::count_bits_flip::countBitsFlip(11, 8) == 2);
+    // A = 21, B = 22 return 2
+    assert(bit_manipulation::count_bits_flip::countBitsFlip(21, 22) == 2);
+    // A = 7, B = 786 return 5
+    assert(bit_manipulation::count_bits_flip::countBitsFlip(7, 786) == 5);
+    std::cout << "All test cases successfully passed!" << std::endl;
+}
+/**
+ * @brief Main function
+ * @returns 0 on exit
+ */
+int main() {
+    test();  // run self-test implementations
+    return 0;
+}