Today I have done leetcode's November LeetCoding Challenge with cpp.

November LeetCoding Challenge 25

Description

Sum of Absolute Differences in a Sorted Array

You are given an integer array nums sorted in non-decreasing order.

Build and return an integer array result with the same length as nums such that result[i] is equal to the summation of absolute differences between nums[i] and all the other elements in the array.

In other words, result[i] is equal to sum(|nums[i]-nums[j]|) where 0 <= j < nums.length and j != i (0-indexed).

Example 1:

Input: nums = [2,3,5]
Output: [4,3,5]
Explanation: Assuming the arrays are 0-indexed, then
result[0] = |2-2| + |2-3| + |2-5| = 0 + 1 + 3 = 4,
result[1] = |3-2| + |3-3| + |3-5| = 1 + 0 + 2 = 3,
result[2] = |5-2| + |5-3| + |5-5| = 3 + 2 + 0 = 5.

Example 2:

Input: nums = [1,4,6,8,10]
Output: [24,15,13,15,21]

Constraints:

• 2 <= nums.length <= 105
• 1 <= nums[i] <= nums[i + 1] <= 104

Solution

class Solution {
public:
  vector<int> getSumAbsoluteDifferences(vector<int>& nums) {
    int back = accumulate(nums.begin(), nums.end(), 0);
    int front = 0; 
    int len = nums.size();
    int count = 0;
    vector<int> answer;
    answer.reserve(len);

    for(auto n : nums) {
      answer.push_back(count * n - front + back - (len - count) * n);
      front += n;
      back -= n;
      count += 1;
    }

    return answer;
  }
};

// Accepted
// 59/59 cases passed (80 ms)
// Your runtime beats 94.05 % of cpp submissions
// Your memory usage beats 66.49 % of cpp submissions (83.6 MB)