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C / C++ Program for Largest Sum Contiguous Subarray

  • Last Updated : 12 Dec, 2018

Write an efficient program to find the sum of contiguous subarray within a one-dimensional array of numbers which has the largest sum.

kadane-algorithm

Recommended: Please solve it on “PRACTICE ” first, before moving on to the solution.

C++




// C++ program to print largest contiguous array sum
#include <climits>
#include <iostream>
using namespace std;
  
int maxSubArraySum(int a[], int size)
{
    int max_so_far = INT_MIN, max_ending_here = 0;
  
    for (int i = 0; i < size; i++) {
        max_ending_here = max_ending_here + a[i];
        if (max_so_far < max_ending_here)
            max_so_far = max_ending_here;
  
        if (max_ending_here < 0)
            max_ending_here = 0;
    }
    return max_so_far;
}
  
/*Driver program to test maxSubArraySum*/
int main()
{
    int a[] = { -2, -3, 4, -1, -2, 1, 5, -3 };
    int n = sizeof(a) / sizeof(a[0]);
    int max_sum = maxSubArraySum(a, n);
    cout << "Maximum contiguous sum is " << max_sum;
    return 0;
}
Output:
Maximum contiguous sum is 7

Above program can be optimized further, if we compare max_so_far with max_ending_here only if max_ending_here is greater than 0.

C++




int maxSubArraySum(int a[], int size)
{
    int max_so_far = 0, max_ending_here = 0;
    for (int i = 0; i < size; i++) {
        max_ending_here = max_ending_here + a[i];
        if (max_ending_here < 0)
            max_ending_here = 0;
  
        /* Do not compare for all elements. Compare only   
          when  max_ending_here > 0 */
        else if (max_so_far < max_ending_here)
            max_so_far = max_ending_here;
    }
    return max_so_far;
}

Please refer complete article on Largest Sum Contiguous Subarray for more details!

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