[Leetcode 53, medium] Maximal subarray

Problem:

Find the contiguous subarray within an array (containing at least one number) which has the largest sum.

For example, given the array

[−2,1,−3,4,−1,2,1,−5,4]

,

the contiguous subarray

[4,−1,2,1]

has the largest sum =

6

.

click to show more practice.

More practice:
If you have figured out the O(n) solution, try coding another solution using the divide and conquer approach, which is more subtle.

Analysis:

Solutions:

C++:

int maxSubArray(int A[], int n) {
        int max_sum = 0;
        int partial_sum = 0;
        for(int i = 0; i < n; ++i) {
            partial_sum += A[i];

            if(i == 0 || partial_sum > max_sum)
                max_sum = partial_sum;

            if(partial_sum < 0)
                partial_sum = 0;
        }
        
        return max_sum;
    }

Java:

Python: