Max double slice sum

Question

Recently, I tried to solve the Max Double Slice Sum problem in codility which is a variant of max slice problem. My Solution was to look for a slice that has maximum value w

Answer 1

Here is an alternative solution to the proposed by me before, more readable and understandable:

int solution(vector & A){
if(A.size() < 4 )
    return 0;
int maxSum = 0;
int sumLeft = 0;
unordered_map leftSums;
leftSums[0] = 0;
for(int i = 2; i < A.size()-1; i++){
    sumLeft += A[i-1];
    if(sumLeft < 0)
        sumLeft = 0;
    leftSums[i-1] =  sumLeft;
}

int sumRight = 0;
unordered_map rightSums;
rightSums[A.size()-1] =  sumRight;
for( int i = A.size() - 3; i >= 1; i--){
    sumRight += A[i+1];
    if(sumRight < 0)
        sumRight = 0;
    rightSums[i+1] = sumRight;
}

for(long i = 1; i < A.size() - 1; i++){
    if(leftSums[i-1] + rightSums[i+1] > maxSum)
        maxSum = leftSums[i-1] + rightSums[i+1];
}
return maxSum;

}