sparse-bin-mat 0.7.0

A sparse implementation of a binary matrix optimized for row operations
Documentation 
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use super::SparseBinMat;

// This assume that the value at the given position is zero before the update
// and that row and column are inbound.
pub(super) fn insert_one_at(mut matrix: SparseBinMat, row: usize, column: usize) -> SparseBinMat {
    matrix = update_column_indices_to_insert_one_at(matrix, row, column);
    increase_row_ranges_after(matrix, row)
}

fn update_column_indices_to_insert_one_at(
    mut matrix: SparseBinMat,
    row: usize,
    column: usize,
) -> SparseBinMat {
    let row_start = matrix.row_ranges[row];
    let row_end = matrix.row_ranges[row + 1];
    let offset = &matrix.column_indices[row_start..row_end]
        .iter()
        .position(|col| *col > column)
        .unwrap_or(row_end - row_start);
    let position = row_start + offset;
    matrix.column_indices.insert(position, column);
    matrix
}

fn increase_row_ranges_after(mut matrix: SparseBinMat, row: usize) -> SparseBinMat {
    for row_range in matrix.row_ranges[row + 1..].iter_mut() {
        *row_range += 1;
    }
    matrix
}

// This assume that the value at the given position is one before the update
// and that row and column are inbound.
pub(super) fn remove_one_at(mut matrix: SparseBinMat, row: usize, column: usize) -> SparseBinMat {
    matrix = update_column_indices_to_remove_one_at(matrix, row, column);
    decrease_row_ranges_after(matrix, row)
}

fn update_column_indices_to_remove_one_at(
    mut matrix: SparseBinMat,
    row: usize,
    column: usize,
) -> SparseBinMat {
    let row_start = matrix.row_ranges[row];
    let row_end = matrix.row_ranges[row + 1];
    let offset = &matrix.column_indices[row_start..row_end]
        .iter()
        .position(|col| *col == column)
        .expect("[Bug - Please report]");
    let position = row_start + offset;
    matrix.column_indices.remove(position);
    matrix
}

fn decrease_row_ranges_after(mut matrix: SparseBinMat, row: usize) -> SparseBinMat {
    for row_range in matrix.row_ranges[row + 1..].iter_mut() {
        *row_range -= 1;
    }
    matrix
}

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn insert_one_at_start_of_row() {
        let mut matrix =
            SparseBinMat::new(4, vec![vec![0, 3], vec![1, 3], vec![0, 1, 3], vec![1, 2]]);

        matrix = insert_one_at(matrix, 1, 0);

        let expected_matrix = SparseBinMat::new(
            4,
            vec![vec![0, 3], vec![0, 1, 3], vec![0, 1, 3], vec![1, 2]],
        );

        assert_eq!(matrix, expected_matrix);
    }

    #[test]
    fn insert_one_at_end_of_row() {
        let mut matrix =
            SparseBinMat::new(4, vec![vec![0, 3], vec![1, 3], vec![0, 1, 3], vec![1, 2]]);

        matrix = insert_one_at(matrix, 3, 3);

        let expected_matrix = SparseBinMat::new(
            4,
            vec![vec![0, 3], vec![1, 3], vec![0, 1, 3], vec![1, 2, 3]],
        );

        assert_eq!(matrix, expected_matrix);
    }

    #[test]
    fn insert_two_ones_in_middle_or_row() {
        let mut matrix =
            SparseBinMat::new(4, vec![vec![0, 3], vec![1, 3], vec![0, 1, 3], vec![1, 2]]);

        matrix = insert_one_at(matrix, 0, 2);
        matrix = insert_one_at(matrix, 0, 1);

        let expected_matrix = SparseBinMat::new(
            4,
            vec![vec![0, 1, 2, 3], vec![1, 3], vec![0, 1, 3], vec![1, 2]],
        );

        assert_eq!(matrix, expected_matrix);
    }

    #[test]
    fn remove_one_at_start_of_row() {
        let mut matrix =
            SparseBinMat::new(4, vec![vec![0, 3], vec![1, 3], vec![0, 1, 3], vec![1, 2]]);

        matrix = remove_one_at(matrix, 2, 0);

        let expected_matrix =
            SparseBinMat::new(4, vec![vec![0, 3], vec![1, 3], vec![1, 3], vec![1, 2]]);

        assert_eq!(matrix, expected_matrix);
    }

    #[test]
    fn remove_one_at_end_of_row() {
        let mut matrix =
            SparseBinMat::new(4, vec![vec![0, 3], vec![1, 3], vec![0, 1, 3], vec![1, 2]]);

        matrix = remove_one_at(matrix, 1, 3);

        let expected_matrix =
            SparseBinMat::new(4, vec![vec![0, 3], vec![1], vec![0, 1, 3], vec![1, 2]]);

        assert_eq!(matrix, expected_matrix);
    }

    #[test]
    fn remove_two_ones_in_middle_or_row() {
        let mut matrix =
            SparseBinMat::new(4, vec![vec![0, 3], vec![1, 3], vec![0, 1, 3], vec![1, 2]]);

        matrix = remove_one_at(matrix, 3, 2);
        matrix = remove_one_at(matrix, 3, 1);

        let expected_matrix =
            SparseBinMat::new(4, vec![vec![0, 3], vec![1, 3], vec![0, 1, 3], vec![]]);

        assert_eq!(matrix, expected_matrix);
    }
}