Merge branch 'master' into feat/grid_unique_path

Author: realstealthninja

bit_manipulation/check_even_odd.cpp

@@ -0,0 +1,93 @@
+/**
+ * @file
+ * @brief Implementation to [Check if a number is Even or Odd using Bitwise Operator]
+ * (https://www.log2base2.com/c-examples/bitwise/odd-or-even-program-in-c-using-bitwise-operator.html)
+ *
+ * @details
+ * Given an integer N, determine whether it is even or odd using bitwise manipulation.
+ * The least significant bit (LSB) of a binary number determines its parity:
+ * - If the LSB is 0, the number is even.
+ * - If the LSB is 1, the number is odd.
+ *
+ * This can be checked efficiently using the bitwise AND operator (&) with 1.
+ * - If (N & 1) == 0, N is even.
+ * - If (N & 1) == 1, N is odd.
+ *
+ * Example:
+ * Consider 8-bit binary representations of two numbers:
+ *     Number: 10 (decimal) -> 00001010 (binary)
+ *       LSB = 0 -> Even number
+ * 
+ *     Number: 13 (decimal) -> 00001101 (binary)
+ *       LSB = 1 -> Odd number
+ *
+ * In both cases, evaluating (N & 1) isolates the LSB:
+ * - For 10: 00001010 & 00000001 = 0  (Even)
+ * - For 13: 00001101 & 00000001 = 1  (Odd)
+ *
+ * Worst Case Time Complexity: O(1)
+ * Space Complexity: O(1)
+ *
+ * @author [Vedant Mukhedkar](https://github.com/git5v)
+ */
+
+#include <cassert>   /// for assert
+#include <cstdint>   /// for uint32_t
+#include <iostream>  /// for IO operations
+#include <string>    /// for std::string
+
+/**
+ * @namespace bit_manipulation
+ * @brief Bit manipulation algorithms
+ */
+namespace bit_manipulation {
+/**
+ * @namespace even_odd
+ * @brief Functions for checking if a number is even or odd using bitwise operations
+ */
+namespace even_odd {
+
+/**
+ * @brief Checks if a number is even or odd using bitwise AND.
+ * @param N The number to check.
+ * @returns "Even" if N is even, "Odd" if N is odd.
+     */
+        bool is_even(std::int64_t N) {
+            return (N & 1) == 0 ? true : false;
+        }
+
+    }  // namespace even_odd
+}  // namespace bit_manipulation
+
+/**
+ * @brief Self-test implementations
+ * @returns void
+ */
+static void test() {
+    using bit_manipulation::even_odd::is_even;
+
+    // Test Even numbers
+    assert(is_even(0) == true);
+    assert(is_even(2) == true);
+    assert(is_even(100) == true);
+    assert(is_even(-4) == true);
+    assert(is_even(-1000) == true);
+
+    // Test Odd numbers
+    assert(is_even(1) == false);
+    assert(is_even(3) == false);
+    assert(is_even(101) == false);
+    assert(is_even(-5) == false);
+    assert(is_even(-999) == false);
+
+    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;
+}

bit_manipulation/count_of_set_bits.cpp

@@ -36,11 +36,19 @@ namespace count_of_set_bits {
  * @returns total number of set-bits in the binary representation of number `n`
  */
 std::uint64_t countSetBits(
-    std ::int64_t n) {  // int64_t is preferred over int so that
+    std ::uint64_t n) {  // uint64_t is preferred over int so that
                         // no Overflow can be there.
+                        //It's preferred over int64_t because it Guarantees that inputs are always non-negative, 
+                        //which matches the algorithmic problem statement.
+                        //set bit counting is conceptually defined only for non-negative numbers.
+                        //Provides a type Safety: Using an unsigned type helps prevent accidental negative values,
+
+    std::uint64_t count = 0;  // "count" variable is used to count number of set-bits('1')
+                            // in binary representation of number 'n'
+                            //Count is uint64_t because it Prevents theoretical overflow if someone passes very large integers.
+                            //  Behavior stays the same for all normal inputs.
+                            // Safer for edge cases.
 
-    int count = 0;  // "count" variable is used to count number of set-bits('1')
-                    // in binary representation of number 'n'
     while (n != 0) {
         ++count;
         n = (n & (n - 1));

others/postfix_evaluation.cpp

@@ -1,6 +1,7 @@
 /**
  * @file
- * @brief Evaluation of [Postfix Expression](https://en.wikipedia.org/wiki/Reverse_Polish_notation)
+ * @brief Evaluation of [Postfix
+ * Expression](https://en.wikipedia.org/wiki/Reverse_Polish_notation)
  * @author [Darshana Sarma](https://github.com/Darshana-Sarma)
  * @details
  * Create a stack to store operands (or values).
@@ -11,10 +12,11 @@
  * When the expression is ended, the number in the stack is the final answer
  */
 #include <algorithm>  // for all_of
-#include <array>      // for std::array
 #include <cassert>    // for assert
 #include <iostream>   // for io operations
+#include <stack>      // for std::stack
 #include <string>     // for stof
+#include <vector>     // for std::vector
 
 /**
  * @namespace others
@@ -26,36 +28,6 @@ namespace others {
  * @brief Functions for Postfix Expression algorithm
  */
 namespace postfix_expression {
- /**
- * @brief Creates an array to be used as stack for storing values
- */
-class Stack {
- public:
-    std::array<float, 20> stack{}; ///< Array which will be used to store numbers in the input
-    int stackTop = -1;            ///< Represents the index of the last value added to array. -1 means array is empty
-};
-
-/**
- * @brief Pushing operand, also called the number in the array to the stack
- * @param operand float value from the input array or evaluation
- * @param stack stack containing numbers
- * @returns none
- */
-void push(float operand, Stack *stack) {
-    stack->stackTop++;
-    stack->stack[stack->stackTop] = operand;
-}
-
-/**
- * @brief Popping operand, also called the number from the stack
- * @param stack stack containing numbers
- * @returns operand float on top of stack
- */
-float pop(Stack *stack) {
-    float operand = stack->stack[stack->stackTop];
-    stack->stackTop--;
-    return operand;
-}
 
 /**
  * @brief Checks if scanned string is a number
@@ -74,28 +46,29 @@ bool is_number(const std::string &s) {
  * @param stack containing numbers
  * @returns none
  */
-void evaluate(float a, float b, const std::string &operation, Stack *stack) {
+void evaluate(float a, float b, const std::string &operation,
+              std::stack<float> &stack) {
     float c = 0;
     const char *op = operation.c_str();
     switch (*op) {
         case '+':
-            c = a + b; // Addition of numbers
-            others::postfix_expression::push(c, stack);
+            c = a + b;  // Addition of numbers
+            stack.push(c);
             break;
 
         case '-':
-            c = a - b; // Subtraction of numbers
-            others::postfix_expression::push(c, stack);
+            c = a - b;  // Subtraction of numbers
+            stack.push(c);
             break;
 
         case '*':
-            c = a * b; // Multiplication of numbers
-            others::postfix_expression::push(c, stack);
+            c = a * b;  // Multiplication of numbers
+            stack.push(c);
             break;
 
         case '/':
-            c = a / b; // Division of numbers
-            others::postfix_expression::push(c, stack);
+            c = a / b;  // Division of numbers
+            stack.push(c);
             break;
 
         default:
@@ -104,47 +77,54 @@ void evaluate(float a, float b, const std::string &operation, Stack *stack) {
     }
 }
 
+namespace {
+float remove_from_stack(std::stack<float> &stack) {
+    if (stack.empty()) {
+        throw std::invalid_argument("Not enough operands");
+    }
+    const auto res = stack.top();
+    stack.pop();
+    return res;
+}
+}  // namespace
+
 /**
  * @brief Postfix Evaluation algorithm to compute the value from given input
  * array
- * @tparam N number of array size
- * @param input Array of characters consisting of numbers and operations
+ * @param input vector of strings consisting of numbers and operations
  * @returns stack[stackTop] returns the top value from the stack
  */
-template <std::size_t N>
-float postfix_evaluation(std::array<std::string, N> input) {
-    Stack stack;
-    int j = 0;
+float postfix_evaluation(const std::vector<std::string> &input) {
+    std::stack<float> stack;
 
-    while (j < N) {
-        std::string scan = input[j];
+    for (const auto &scan : input) {
         if (is_number(scan)) {
-            push(std::stof(scan), &stack);
+            stack.push(std::stof(scan));
 
         } else {
-            float op2 = pop(&stack);
-            float op1 = pop(&stack);
+            const auto op2 = remove_from_stack(stack);
+            const auto op1 = remove_from_stack(stack);
 
-            evaluate(op1, op2, scan, &stack);
+            evaluate(op1, op2, scan, stack);
         }
-        j++;
     }
 
-    std::cout << stack.stack[stack.stackTop] << "\n";
-
-    return stack.stack[stack.stackTop];
+    const auto res = remove_from_stack(stack);
+    if (!stack.empty()) {
+        throw std::invalid_argument("Too many operands");
+    }
+    return res;
 }
 }  // namespace postfix_expression
 }  // namespace others
 
-
 /**
  * @brief Test function 1 with input array
  * {'2', '3', '1', '*', '+', '9', '-'}
  * @returns none
  */
 static void test_function_1() {
-    std::array<std::string, 7> input = {"2", "3", "1", "*", "+", "9", "-"};
+    std::vector<std::string> input = {"2", "3", "1", "*", "+", "9", "-"};
 
     float answer = others::postfix_expression::postfix_evaluation(input);
 
@@ -153,24 +133,80 @@ static void test_function_1() {
 
 /**
  * @brief Test function 2 with input array
- * {'1', '2', '+', '2', '/', '5', '*', '7', '+'}
+ * {'100', '200', '+', '2', '/', '5', '*', '7', '+'}
  * @returns none
  */
 static void test_function_2() {
-    std::array<std::string, 9> input = {"100", "200", "+", "2", "/",
-                                        "5",   "*",   "7", "+"};
+    std::vector<std::string> input = {"100", "200", "+", "2", "/",
+                                      "5",   "*",   "7", "+"};
     float answer = others::postfix_expression::postfix_evaluation(input);
 
     assert(answer == 757);
 }
 
+static void test_function_3() {
+    std::vector<std::string> input = {
+        "1", "1", "1", "1", "1", "1", "1", "1", "1", "1", "1",
+        "1", "1", "1", "1", "1", "1", "1", "1", "1", "1", "1",
+        "+", "+", "+", "+", "+", "+", "+", "+", "+", "+", "+",
+        "+", "+", "+", "+", "+", "+", "+", "+", "+", "+"};
+    float answer = others::postfix_expression::postfix_evaluation(input);
+
+    assert(answer == 22);
+}
+
+static void test_single_input() {
+    std::vector<std::string> input = {"1"};
+    float answer = others::postfix_expression::postfix_evaluation(input);
+
+    assert(answer == 1);
+}
+
+static void test_not_enough_operands() {
+    std::vector<std::string> input = {"+"};
+    bool throws = false;
+    try {
+        others::postfix_expression::postfix_evaluation(input);
+    } catch (std::invalid_argument &) {
+        throws = true;
+    }
+    assert(throws);
+}
+
+static void test_not_enough_operands_empty_input() {
+    std::vector<std::string> input = {};
+    bool throws = false;
+    try {
+        others::postfix_expression::postfix_evaluation(input);
+    } catch (std::invalid_argument &) {
+        throws = true;
+    }
+    assert(throws);
+}
+
+static void test_too_many_operands() {
+    std::vector<std::string> input = {"1", "2"};
+    bool throws = false;
+    try {
+        others::postfix_expression::postfix_evaluation(input);
+    } catch (std::invalid_argument &) {
+        throws = true;
+    }
+    assert(throws);
+}
+
 /**
  * @brief Main function
  * @returns 0 on exit
  */
 int main() {
     test_function_1();
     test_function_2();
+    test_function_3();
+    test_single_input();
+    test_not_enough_operands();
+    test_not_enough_operands_empty_input();
+    test_too_many_operands();
 
     std::cout << "\nTest implementations passed!\n";