You are given the number of rows n_rows and number of columns n_cols of a 2D binary matrix where all values are initially 0. Write a function flip which chooses a 0 value uniformly at random, changes it to 1, and then returns the position [row.id, col.id] of that value. Also, write a function reset which sets all values back to 0. Try to minimize the number of calls to system's Math.random() and optimize the time and space complexity. Note: 1 <= n_rows, n_cols <= 10000 0 <= row.id < n_rows and 0 <= col.id < n_cols flip will not be called when the matrix has no 0 values left. the total number of calls to flip and reset will not exceed 1000. Example 1: Input: ["Solution","flip","flip","flip","flip"] [[2,3],[],[],[],[]] Output: [null,[0,1],[1,2],[1,0],[1,1]] Example 2: Input: ["Solution","flip","flip","reset","flip"] [[1,2],[],[],[],[]] Output: [null,[0,0],[0,1],null,[0,0]] Explanation of Input Syntax: The input is two lists: the subroutines called and their arguments. Solution's constructor has two arguments, n_rows and n_cols. flip and reset have no arguments. Arguments are always wrapped with a list, even if there aren't any.