Leetcode 370. 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.

Code (Java):

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class Solution {     public int[] getModifiedArray(int length, int[][] updates) {         int[] ans = new int[length];                   for (int[] update : updates) {             int start = update[0];             int end = update[1];             int inc = update[2];                           ans[start] += inc;             if (end + 1 < length) {                 ans[end + 1] += -inc;             }         }           for (int i = 1; i < length; i++) {             ans[i] += ans[i -1];         }                   return ans;     } }

Analysis:
Time complexity: O(n + k), where n is the length, and k is the number of update operations.