Maximum Sum Subarray with Equal Endpoints

Problem: Maximum Subarray Sum with Equal Endpoints Given an integer array a, find a pair of indices (i, j) such that: 0 <= i <= j < n a[i] == a[j] Among all such pairs, maximize the subarray sum: S(i,j) = a[i] + a[i+1] + ... + a[j] Return the indices i j that achieve the maximum sum. If multiple pairs achieve the same maximum sum, you may return any of them. Constraints 1 <= n <= 2e5 -1e9 <= a[i] <= 1e9 Follow-up Keep extra space strictly O(1) (excluding the input array). You may allow higher time complexity (e.g., O(n log n) or O(n^2)), but additional memory must remain constant. Examples / Tests a = [1, 2, 3, 1] → best i=0, j=3, sum = 7 a = [5] → i=0, j=0, sum = 5 a = [2, -1, 2] → i=0, j=2, sum = 3 a = [1, -100, 1, 1] → one best is i=2, j=3, sum = 2 a = [3, 3, -10, 3] → best could be i=0, j=1, sum = 6 Example Input 4 1 2 3 1 Output 0 3