flip_matrix.txt

519. Random Flip Matrix
/*
There is an m x n binary grid matrix with all the values set 0 initially.
Design an algorithm to randomly pick an index (i, j) where matrix[i][j] == 0 and flips it to 1.
All the indices (i, j) where matrix[i][j] == 0 should be equally likely to be returned.
Optimize your algorithm to minimize the number of calls made to the built-in random function of
your language and optimize the time and space complexity.

Implement the Solution class:

Solution(int m, int n) Initializes the object with the size of the binary matrix m and n.
int[] flip() Returns a random index [i, j] of the matrix where matrix[i][j] == 0 and flips it to 1.
void reset() Resets all the values of the matrix to be 0.
*\

class Solution {
public:
    int m,n;
    int i = 0, j = 0;
    Solution(int m, int n) {
        this -> m = m;
        this -> n = n;
    }
    
    vector<int> flip() {
        int I = i , J = j;
        if(j + 1 < n){
            j++;
        }
        else if(i + 1 < m){
            i++;
            j = 0;
        }
        else{
            i = 0;
            j = 0;
        }
        return {I,J};
    }
    
    void reset() {
        
    }
};