diff --git a/others/kadanes.cpp b/others/kadanes.cpp new file mode 100644 index 000000000..399c7e1c9 --- /dev/null +++ b/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 // for assert +#include // for io operations +#include // 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; +} \ No newline at end of file