Left and Right Sum Differences

Problem Statement - link #

Given a 0-indexed integer array nums, find a 0-indexed integer array answer where:

• answer.length == nums.length.

• answer[i] =

  leftSum[i] - rightSum[i]

  .

Where:

• leftSum[i] is the sum of elements to the left of the index i in the array nums. If there is no such element, leftSum[i] = 0.
• rightSum[i] is the sum of elements to the right of the index i in the array nums. If there is no such element, rightSum[i] = 0.

Return the array answer.

Examples #

Example 1:

Input: nums = [10,4,8,3]
Output: [15,1,11,22]
Explanation: The array leftSum is [0,10,14,22] and the array rightSum is [15,11,3,0].
The array answer is [|0 - 15|,|10 - 11|,|14 - 3|,|22 - 0|] = [15,1,11,22].

Example 2:

Input: nums = [1]
Output: [0]
Explanation: The array leftSum is [0] and the array rightSum is [0].
The array answer is [|0 - 0|] = [0].

Constraints #

• 1 <= nums.length <= 1000
• 1 <= nums[i] <= 10^5

Solutions #

class Solution {
public:
    vector<int> leftRigthDifference(vector<int>& nums) {
        int total_sum = accumulate(nums.begin(), nums.end(), 0);
        int cur_sum = 0;
        vector<int> res;
        for(int &i: nums) {
            total_sum -= i;
            res.push_back(abs(total_sum - cur_sum));
            cur_sum += i;
        }
        return res;
    }
}