02CreateIndexesofSubarraySum

Indexes of Subarray Sum
Difficulty: MediumAccuracy: 16.5%Submissions: 1.7MPoints: 4
Given an array arr[] containing only non-negative integers, your task is to find a continuous subarray (a contiguous sequence of elements) whose sum equals a specified value target. You need to return the 1-based indices of the leftmost and rightmost elements of this subarray. You need to find the first subarray whose sum is equal to the target.

Note: If no such array is possible then, return [-1].

Examples:

Input: arr[] = [1, 2, 3, 7, 5], target = 12
Output: [2, 4]
Explanation: The sum of elements from 2nd to 4th position is 12.
Input: arr[] = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], target = 15
Output: [1, 5]
Explanation: The sum of elements from 1st to 5th position is 15.
Input: arr[] = [5, 3, 4], target = 2
Output: [-1]
Explanation: There is no subarray with sum 2.
Constraints:
1 <= arr.size()<= 106
0 <= arr[i] <= 103
0 <= target <= 109


class Solution {
    static ArrayList<Integer> subarraySum(int[] arr, int target) {
        int s = 0, e = 0;
        int curr = 0;
        ArrayList<Integer> res = new ArrayList<>();

        for (int i = 0; i < arr.length; i++) {
            curr += arr[i];
            if (curr >= target) {
                e = i;
                while (curr > target && s < e) {
                    curr -= arr[s];
                    s++;
                }
                if (curr == target) {
                    res.add(s + 1);
                    res.add(e + 1);
                    return res;
                }
            }
        }
        res.add(-1);
        return res;
    }
}