Из матрицы инцидентности в матрицу смежности или в список смежности

#include <vector>
#include <cassert>
#include <iostream>
 
typedef std::vector<bool> matrix_row;
typedef std::vector<matrix_row> matrix; 
 
matrix adj = 
{
    { 1, 1, 1, 0 },
    { 1, 0, 0, 1 },
    { 1, 0, 0, 1 },
    { 0, 1, 1, 0 }
};
 
//В инцидентность
matrix adjacency_to_incidence(const matrix &adj)
{
    int cols = adj.size();
    assert(cols > 0);
 
    int rows = adj[0].size();
    assert(rows > 0);
 
    assert(rows == cols);
 
    int edge = 0;
    matrix incidence;
 
    for (int col = 0; col < cols; ++col) {
        for (int row = 0; row <= col; ++row) {
            if (adj[col][row]) {
                incidence.push_back(matrix_row(cols, 0));
                incidence[edge][row] = incidence[edge][col] = 1;
                ++edge;
            }
        }
    }
 
    return incidence;
}
 
//В смежность
matrix incidence_to_adjacency(const matrix &inc)
{
    int edges = inc.size();
    assert(edges > 0);
 
    int vertices = inc[0].size();
    assert(vertices > 0);
 
    matrix adjacency(vertices, matrix_row(vertices, 0));
 
    for (int edge = 0; edge < edges; ++edge) {
        int a = -1, b = -1, vertex = 0;
        for (; vertex < vertices && a == -1; ++vertex) {
            if (inc[edge][vertex]) a = vertex;
        }
        for (; vertex < vertices && b == -1; ++vertex) {
            if (inc[edge][vertex]) b = vertex;
        }
        if (b == -1) b = a;
        adjacency[a][b] = adjacency[b][a] = 1;
    }
 
    return adjacency;
}
 
void print_matrix(const matrix &m)
{
    int cols = m.size();
    if (cols == 0) return;
    int rows = m[0].size();
    if (rows == 0) return;
 
    for (int c = 0; c < cols; ++c) {
        for (int r = 0; r < rows; ++r) {
            std::cout << m[c][r] << " ";
        }
        std::cout << std::endl;
    }
    std::cout << std::endl;
}
 
int main()
{
    matrix incidence = adjacency_to_incidence(adj);
    print_matrix(incidence);
 
    matrix adjacency = incidence_to_adjacency(incidence);
    print_matrix(adjacency);
 
    return 0;
}