Range Addition 1

Description
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.


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 :



class Solution {
public:
    vector<int> getModifiedArray(int length, vector<vector<int>> &updates) {
        vector<int> ans(length, 0);

        for(int i=0; i<updates.size(); i++){
            int s = updates[i][0], e = updates[i][1], val = updates[i][2];
            ans[s] += val;
            if(e+1<length)  ans[e+1] += -val;
        }

        for(int i=1; i<length; i++){
            ans[i] += ans[i-1];
        }
        return ans;
    }
};