matrix_flatten.cpp

matrix_flatten.cpp

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

/*
 * Returning the index in the flatten matrix for n by m by p matrix.
 *
 * @param n dimention 1 of 3d matrix
 * @param m dimention 2 of 3d matrix
 * @param p dimention 3 of 3d matrix
 *
 * @return vector<int> vector of size q the size of the flatten matrix.
 */
vector<int> create_flatten_vector(int n, int m, int p){
    long q = 1L*n*m*p;
    return vector<int>(q);
}

/*
 * Returning the index in the flatten matrix for n by m by p matrix.
 *
 * @param n dimention 1 of 3d matrix
 * @param m dimention 2 of 3d matrix
 * @param p dimention 3 of 3d matrix
 *
 * @param i index 0 of 3d matrix
 * @param j index 1 of 3d matrix
 * @param k index 2 of 3d matrix
 *
 * @return y index in the flatten matrix
 * */
long get_flatten_idx(int n, int m, int p, int i, int j, int k){
    vector<int> input {n, m, p, i, j, k};
    if(any_of(input.begin(), input.end(), [](int x){ return x < 0; })){
        return -1;
    }
    long y = (1L*i*m*p) + (j*p) + (k);
    return y;
}

int main() {
    vector<vector<vector<int>>> matrix3D {
        { {1, 2}, {3,   4} },
        { {4, 5}, {6,   7} },
        { {8, 9}, {10, 11} }
    };

    int n = matrix3D.size(), m = matrix3D[0].size(), p = matrix3D[0][0].size();
    vector<int> flatten = create_flatten_vector(n, m, p);

    for(int i = 0; i < matrix3D.size(); i++){
        for(int j = 0; j < matrix3D[i].size(); j++){
            for(int k = 0; k < matrix3D[i][j].size(); k++){
                long y = get_flatten_idx(n, m, p, i, j, k);
                flatten[y] = matrix3D[i][j][k];
            }
        }
    }

    for(int x : flatten){
        cout << x << endl;
    }
	return 0;
}