LeetCode-Range Addition

Assume you have an array of length n initialized with all 0's and are given k update operations.

Each operation is represented as a triplet: [startIndex, endIndex, inc] which increments each element of subarray A[startIndex ... endIndex] (startIndex and endIndex inclusive) with inc.

Return the modified array after all k operations were executed.

Example:

Given:

    length = 5,
    updates = [
        [1,  3,  2],
        [2,  4,  3],
        [0,  2, -2]
    ]

Output:

    [-2, 0, 3, 5, 3]

Explanation:

Initial state:
[ 0, 0, 0, 0, 0 ]

After applying operation [1, 3, 2]:
[ 0, 2, 2, 2, 0 ]

After applying operation [2, 4, 3]:
[ 0, 2, 5, 5, 3 ]

After applying operation [0, 2, -2]:
[-2, 0, 3, 5, 3 ]

Solution:

public class Solution {
    public int[] getModifiedArray(int length, int[][] updates) {
        int[] res = new int[length];
        Arrays.fill(res,0);
        for (int[] update : updates){
            int start = update[0];
            int end = update[1]+1;
            int val = update[2];

            res[start] += val;
            if (end<length){
                res[end] -= val;
            }
        }

        int sum = 0;
        for (int i=0;i<length;i++){
            sum += res[i];
            res[i] = sum;
        }
        return res;
    }
}