pair_graph.hpp

#pragma once

#include <memory>
#include <vector>

class PairGraph
{
public:
  PairGraph(int nrows, int ncols) : nrows(nrows), ncols(ncols)
  {
    this->rows.resize(nrows);
    this->cols.resize(ncols);
  }

  /**
   * Returns the column index of the pair matching this row
   */
  inline int colForRow(int row) const
  {
    return this->rows[row];
  }

  /**
   * Returns the row index of the pair matching this column
   */
  inline int rowForCol(int col) const
  {
    return this->cols[col];
  }

  /**
   * Creates a pair between row and col
   */
  inline void set(int row, int col)
  {
    this->rows[row] = col;
    this->cols[col] = row;
  }

  inline bool isRowSet(int row) const
  {
    return rows[row] >= 0;
  }

  inline bool isColSet(int col) const
  {
    return cols[col] >= 0;
  }

  inline bool isPair(int row, int col)
  {
    return rows[row] == col;
  }

  /**
   * Clears pair between row and col
   */
  inline void reset(int row, int col)
  {
    this->rows[row] = -1;
    this->cols[col] = -1;
  }

  /**
   * Clears all pairs in graph
   */
  void clear()
  {
    for (int i = 0; i < this->nrows; i++)
    {
      this->rows[i] = -1;
    }
    for (int j = 0; j < this->ncols; j++)
    {
      this->cols[j] = -1;
    }
  }

  int numPairs()
  {
    int count = 0;
    for (int i = 0; i < nrows; i++)
    {
      if (rows[i] >= 0)
      {
        count++;
      }
    }
    return count;
  }

  std::vector<std::pair<int, int>> pairs()
  {
    std::vector<std::pair<int, int>> p(numPairs());
    int count = 0;
    for (int i = 0; i < nrows; i++)
    {
      if (isRowSet(i))
      {
        p[count++] = {i, colForRow(i)};
      }
    }
    return p;
  }

  const int nrows;
  const int ncols;

private:
  std::vector<int> rows;
  std::vector<int> cols;
};