Find Maximum Sum of Strictly Increasing Subarray in C++

Suppose we have an array of n integers. Find the max sum of strictly increasing subarrays. So if the array is like [1, 2, 3, 2, 5, 1, 7], the sum is 8. In this array there are three strictly increasing sub-arrays these are {1, 2, 3}, {2, 5} and {1, 7}. The max sum sub-array is {1, 7}

To solve this problem, we have to keep track of max sum and the current sum. For each element arr[i] if this is larger than arr[i – 1], then we add this to the current sum, otherwise arr[i] is the starting point of another subarray. So we shall update the current sum as array. Before updating current sum, we will update max sum if required.

Example

 Live Demo

#include<iostream>
using namespace std;
int maximum(int a, int b){
   return (a>b)?a:b;
}
int maximum_sum_incr_subarr(int array[] , int n) {
   int max_sum = 0;
   int current_sum = array[0] ;
   for (int i=1; i<n ; i++ ) {
      if (array[i-1] < array[i])
         current_sum = current_sum + array[i];
      else {
         max_sum = maximum(max_sum, current_sum);
         current_sum = array[i];
      }
   }
   return max(max_sum, current_sum);
}
int main() {
   int arr[] = {1, 2, 3, 2, 5, 1, 7};
   int n = sizeof(arr)/sizeof(arr[0]);
   cout << "Maximum sum : " << maximum_sum_incr_subarr(arr , n);
}

Output

Maximum sum : 8