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 operation

minOperations.js

/**
 * This function calculates the minimum number of operations needed 
 * to transform a 2D grid into a uniform grid based on a given step size.
 * If it's not possible, it returns -1.
 * 
 * @param {number[][]} grid - The input 2D grid of numbers.
 * @param {number} x - The step size for allowed operations.
 * @return {number} The minimum number of operations, or -1 if not possible.
 */
var minOperations = function(grid, x) {
    // Flatten the 2D array into a 1D array and sort it in ascending order.
    let arr = grid.flat().sort((a, b) => a - b);
    let len = arr.length;

    // Determine the median value of the sorted array (target number).
    let mid = arr[Math.floor(len / 2)];

    // Validate if transforming the grid is possible. 
    // Check if the difference between consecutive elements is divisible by x.
    for (let i = 1; i < len; i++) {
        if ((arr[i] - arr[i - 1]) % x !== 0) return -1;
    }

    // Calculate the total number of operations needed.
    let ans = 0;
    for (let i = 0; i < len; i++) {
        ans += Math.abs(arr[i] - mid) / x; // Number of steps to move each value to the median.
    }

    return ans;
};