[LintCode/LeetCode] Range Addition

Problem

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]
]

return [-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 {
    /**
     * @param length: the length of the array
     * @param updates: update operations
     * @return: the modified array after all k operations were executed
     */
    public int[] getModifiedArray(int length, int[][] updates) {
        // Write your code here
        
        int[] res = new int[length];
        Arrays.fill(res, 0);
        
        for (int[] update: updates) {
            for (int i = update[0]; i <= update[1]; i++) {
                res[i] += update[2];
            }
        }
        return res;
    }
}