Javascript Program for Size of The Subarray With Maximum Sum

An array is given, find length of the subarray having maximum sum.

Examples : 

Input :  a[] = {1, -2, 1, 1, -2, 1}
Output : Length of the subarray is 2
Explanation: Subarray with consecutive elements 
and maximum sum will be {1, 1}. So length is 2

Input : ar[] = { -2, -3, 4, -1, -2, 1, 5, -3 }
Output : Length of the subarray is 5
Explanation: Subarray with consecutive elements 
and maximum sum will be {4, -1, -2, 1, 5}. 

This problem is mainly a variation of Largest Sum Contiguous Subarray Problem.
The idea is to update starting index whenever sum ending here becomes less than 0.

// JavaScript program to print length
// of the largest contiguous array sum
function maxSubArraySum(a, size) {
    let max_so_far = Number.MIN_VALUE,
        max_ending_here = 0, start = 0,
        end = 0, s = 0;

    for (let i = 0; i < size; i++) {
        max_ending_here += a[i];

        if (max_so_far < max_ending_here) {
            max_so_far = max_ending_here;
            start = s;
            end = i;
        }

        if (max_ending_here < 0) {
            max_ending_here = 0;
            s = i + 1;
        }
    }
    return (end - start + 1);
}

// Driver code
let a = [-2, -3, 4, -1, -2, 1, 5, -3];
let n = a.length;

console.log(maxSubArraySum(a, n));

5

Complexity Analysis:

• Time Complexity: O(N) where N is size of the input array. This is because a for loop is executing from 1 to size of the array.
• Space Complexity: O(1) as no extra space has been used.

Please refer complete article on Size of The Subarray With Maximum Sum for more details!