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

March LeetCoding Challenge 26

Description

Minimum Operations to Make a Uni-Value Grid

You are given a 2D integer grid of size m x n and an integer x. In one operation, you can add x to or subtract x from any element in the grid.

A uni-value grid is a grid where all the elements of it are equal.

Return the minimum number of operations to make the grid uni-value. If it is not possible, return -1.

Example 1:

Input: grid = [[2,4],[6,8]], x = 2
Output: 4
Explanation: We can make every element equal to 4 by doing the following: 
- Add x to 2 once.
- Subtract x from 6 once.
- Subtract x from 8 twice.
A total of 4 operations were used.

Example 2:

Input: grid = [[1,5],[2,3]], x = 1
Output: 5
Explanation: We can make every element equal to 3.

Example 3:

Input: grid = [[1,2],[3,4]], x = 2
Output: -1
Explanation: It is impossible to make every element equal.

Constraints:

• m == grid.length
• n == grid[i].length
• 1 <= m, n <= 105
• 1 <= m * n <= 105
• 1 <= x, grid[i][j] <= 104

Solution

class Solution {
public:
  int minOperations(vector<vector<int>>& grid, int x) {
    int target = grid.front().front() % x;
    vector<int> nums;
    for(auto &row : grid) {
      for(auto n : row) {
        if(n % x != target) return -1;
        nums.push_back(n);
      }
    }

    sort(nums.begin(), nums.end());
    target = nums[nums.size() / 2];
    int answer = 0;
    for(auto n : nums) {
      answer += abs(n - target) / x;
    }

    return answer;
  }
};

// Accepted
// 62/62 cases passed (32 ms)
// Your runtime beats 78.72 % of cpp submissions
// Your memory usage beats 67.78 % of cpp submissions (87.1 MB)