370. Range Addition

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 ]

Credits:Special thanks to @vinod23 for adding this problem and creating all test cases.

Solution

public class Solution {
    public int[] getModifiedArray(int length, int[][] updates) {
        if (length <= 0) return new int[0];
        int[] result = new int[length];

        for(int i = 0; i < updates.length; i ++) {
            int[] current = updates[i];
            int startIndex = current[0];
            int endIndex = current[1];
            int addition = current[2];

            for(int j = startIndex; j <= endIndex; j ++) {
                result[j] += addition;
            }
        }

        return result;
    }
}