feat: kadane's algorithm added

others/kadanes.cpp

@@ -0,0 +1,83 @@
+/**
+ * @file
+ * @brief Efficient implemention for maximum contiguos subarray sum by kadane's algorithm.
+ * @details
+ * Our task is to take length of array and then the whole array as input from
+ * the user and then calculate the maximum contiguos subarray sum for the 
+ * input array, using the kadane's algorithm. 
+ * 
+ * reference article : https://www.geeksforgeeks.org/largest-sum-contiguous-subarray/
+ * 
+ * There can be a case that all the elements in the input array are negative. 
+ * In that case, the least value among all elements is the maximum sum with subarray 
+ * length = 1.
+ * @author [Abhijeet Tiwari](https://github.com/thisabhijeet)
+ */
+
+#include <cassert>  // for assert
+#include <iostream> // for io operations
+#include <climits>  // for INT_MIN value
+using namespace std;
+
+/** max_subarray_sum function
+ * \param arr input array 
+ * \param length length of the input array
+ * \returns maximum contiguous subarray sum
+ */
+
+int max_subarray_sum(int arr[], int length)
+{
+    int current_max = INT_MIN, current_sum = 0;
+    for (int i = 0; i < length; i++)
+    {
+        current_sum = current_sum + arr[i];
+        if (current_max < current_sum)
+        {
+            current_max = current_sum;
+        }
+
+        if (current_sum < 0)
+        {
+            current_sum = 0;
+        }
+    }
+    return current_max;
+}
+
+/**
+ * @brief Self-test implementations
+ * @returns void
+ */
+
+static void test()
+{
+    int arr[4] = {1, 2, 3, 4};
+    int arr1[5] = {-1, -2, -4, -6, 7};
+    assert(max_subarray_sum(arr, 4) == 10);
+    assert(max_subarray_sum(arr1, 5) == 7);
+    cout << "all test cases passed!";
+}
+
+/** main function */
+int main()
+{ // Below is the code for accepting array from user and then calling
+    // the function for the required output.
+    // It has been commented for now so that the test() function can run
+    // and test cases can be verified.
+    // code for accepting array from user starts
+
+    // int n; // variable for length of input array
+    // cout << "Enter length of the array: ";
+    // cin >> n;
+    // int arr[n];
+    // for (int i = 0; i < n; i++) // taking input of each element of the array
+    // {
+    //     cin >> arr[i];
+    // }
+    // int max_sum = max_subarray_sum(arr, n);
+    // cout << "Maximum contiguous sum for this array is : " << max_sum << endl;
+
+    // code for accepting array from user ends
+    test();
+    return 0;
+}