Merge pull request #195 from harshendram/Algo/KadaneAlgo

Added the implementation of kadane algorithm implemented in cpp

Author: Pradeepsingh61

CPP/algorithms/dynamic_programming/kadane_Algorithm.cpp

@@ -0,0 +1,98 @@
+#include <vector>
+#include <algorithm>
+#include <climits>
+#include <iostream>
+
+int kadane(std::vector<int> &nums)
+{
+    if (nums.empty())
+    {
+        return 0;
+    }
+
+    int max_so_far = INT_MIN;
+    int max_ending_here = 0;
+
+    for (int num : nums)
+    {
+        max_ending_here = max_ending_here + num;
+
+        if (max_so_far < max_ending_here)
+        {
+            max_so_far = max_ending_here;
+        }
+
+        if (max_ending_here < 0)
+        {
+            max_ending_here = 0;
+        }
+    }
+
+    if (max_so_far == INT_MIN)
+    {
+        int max_val = nums[0];
+        for (size_t i = 1; i < nums.size(); ++i)
+        {
+            if (nums[i] > max_val)
+            {
+                max_val = nums[i];
+            }
+        }
+        return max_val;
+    }
+
+    return max_so_far;
+}
+
+// A slightly cleaner version that handles all-negative arrays without a separate check.
+int kadane_optimized(std::vector<int> &nums)
+{
+    if (nums.empty())
+    {
+        return 0;
+    }
+
+    int max_so_far = nums[0];
+    int current_max = nums[0];
+
+    for (size_t i = 1; i < nums.size(); ++i)
+    {
+        current_max = std::max(nums[i], current_max + nums[i]);
+        max_so_far = std::max(max_so_far, current_max);
+    }
+
+    return max_so_far;
+}
+
+int main()
+{
+    // Test case 1: Mixed positive and negative numbers
+    std::vector<int> arr1 = {-2, -3, 4, -1, -2, 1, 5, -3};
+    std::cout << "Array 1: [-2, -3, 4, -1, -2, 1, 5, -3]" << std::endl;
+    std::cout << "Maximum subarray sum (kadane): " << kadane(arr1) << std::endl;
+    std::cout << "Maximum subarray sum (optimized): " << kadane_optimized(arr1) << std::endl;
+    std::cout << std::endl;
+
+    // Test case 2: All negative numbers
+    std::vector<int> arr2 = {-5, -2, -8, -1};
+    std::cout << "Array 2: [-5, -2, -8, -1]" << std::endl;
+    std::cout << "Maximum subarray sum (kadane): " << kadane(arr2) << std::endl;
+    std::cout << "Maximum subarray sum (optimized): " << kadane_optimized(arr2) << std::endl;
+    std::cout << std::endl;
+
+    // Test case 3: All positive numbers
+    std::vector<int> arr3 = {1, 2, 3, 4, 5};
+    std::cout << "Array 3: [1, 2, 3, 4, 5]" << std::endl;
+    std::cout << "Maximum subarray sum (kadane): " << kadane(arr3) << std::endl;
+    std::cout << "Maximum subarray sum (optimized): " << kadane_optimized(arr3) << std::endl;
+    std::cout << std::endl;
+
+    // Test case 4: Single element
+    std::vector<int> arr4 = {-3};
+    std::cout << "Array 4: [-3]" << std::endl;
+    std::cout << "Maximum subarray sum (kadane): " << kadane(arr4) << std::endl;
+    std::cout << "Maximum subarray sum (optimized): " << kadane_optimized(arr4) << std::endl;
+    std::cout << std::endl;
+
+    return 0;
+}