RANGE ADDITION (MUST DO) LINE SWEEP PROBLEM

ASKED IN GOOGLE - https://www.lintcode.com/problem/903/

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 ]

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ITS CALLED THE "LINE SWEEP ALGORITHM"

class Solution {
public:
    vector<int> getModifiedArray(int n, vector<vector<int>> &updates) {
        vector<int> res(n,0);
        for(auto update: updates){
            int start=update[0];
            int end=update[1];
            int inc=update[2];
            res[start]+=inc;;
            if(end+1<n){
                res[end+1]-=inc;
            }
        }
        for(int i=1;i<n;i++){
            res[i]+=res[i-1];
        }
        return res;
    }
};