Largest sum subarray with at-least k numbers in C++

C++Server Side ProgrammingProgramming

Let's see the steps to complete the program.

  • Initialise the array.
  • Initialise max_sum array of size n.
  • Find the max sum for every index and store it in max_sum array.
  • Compute the sum of all the elements and store it in a variable sum.
  • Write a loop that iterates from i = k to n.
    • Add a[i] - a[i - k] to the sum.
    • Update the result with max of result, sum.
    • Update the result with max of result, sum + max_sum[i - k].

Example

Let's see the code.

 Live Demo

#include<bits/stdc++.h>
using namespace std;
int getMaxSum(int a[], int n, int k) {
   int maxSum[n];
   maxSum[0] = a[0];
   int currentMax = a[0];
   for (int i = 1; i < n; i++) {
      currentMax = max(a[i], currentMax+a[i]);
      maxSum[i] = currentMax;
   }
   int sum = 0;
   for (int i = 0; i < k; i++) {
      sum += a[i];
   }
   int result = sum;
   for (int i = k; i < n; i++) {
      sum += a[i] - a[i-k];
      result = max(result, sum);
      result = max(result, sum + maxSum[i-k]);
   }
   return result;
}
int main() {
   int a[] = {5, 3, 7, -5, 6, 2, 1};
   int k = 6;
   cout << getMaxSum(a, 7, k) << endl;
   return 0;
}

Output

If you run the above code, then you will get the following result.

19

Conclusion

If you have any queries in the tutorial, mention them in the comment section.

raja
Published on 09-Apr-2021 17:35:37
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