/*
 * Revision Control Information
 *
 * $Source$
 * $Author$
 * $Revision$
 * $Date$
 *
 */
#include "mincov_int.h"

static int visit_col();

static void
copy_row(A, prow)
register sm_matrix *A;
register sm_row *prow;
{
    register sm_element *p;

    for(p = prow->first_col; p != 0; p = p->next_col) {
    (void) sm_insert(A, p->row_num, p->col_num);
    }
}


static int
visit_row(A, prow, rows_visited, cols_visited)
sm_matrix *A;
sm_row *prow;
int *rows_visited;
int *cols_visited;
{
    sm_element *p;
    sm_col *pcol;

    if (! prow->flag) {
    prow->flag = 1;
    (*rows_visited)++;
    if (*rows_visited == A->nrows) {
        return 1;
    }
    for(p = prow->first_col; p != 0; p = p->next_col) {
        pcol = sm_get_col(A, p->col_num);
        if (! pcol->flag) {
        if (visit_col(A, pcol, rows_visited, cols_visited)) {
            return 1;
        }
        }
    }
    }
    return 0;
}


static int
visit_col(A, pcol, rows_visited, cols_visited)
sm_matrix *A;
sm_col *pcol;
int *rows_visited;
int *cols_visited;
{
    sm_element *p;
    sm_row *prow;

    if (! pcol->flag) {
    pcol->flag = 1;
    (*cols_visited)++;
    if (*cols_visited == A->ncols) {
        return 1;
    }
    for(p = pcol->first_row; p != 0; p = p->next_row) {
        prow = sm_get_row(A, p->row_num);
        if (! prow->flag) {
        if (visit_row(A, prow, rows_visited, cols_visited)) {
            return 1;
        }
        }
    }
    }
    return 0;
}

int
sm_block_partition(A, L, R)
sm_matrix *A;
sm_matrix **L, **R;
{
    int cols_visited, rows_visited;
    register sm_row *prow;
    register sm_col *pcol;

    /* Avoid the trivial case */
    if (A->nrows == 0) {
    return 0;
    }

    /* Reset the visited flags for each row and column */
    for(prow = A->first_row; prow != 0; prow = prow->next_row) {
    prow->flag = 0;
    }
    for(pcol = A->first_col; pcol != 0; pcol = pcol->next_col) {
    pcol->flag = 0;
    }

    cols_visited = rows_visited = 0;
    if (visit_row(A, A->first_row, &rows_visited, &cols_visited)) {
    /* we found all of the rows */
    return 0;
    } else {
    *L = sm_alloc();
    *R = sm_alloc();
    for(prow = A->first_row; prow != 0; prow = prow->next_row) {
        if (prow->flag) {
        copy_row(*L, prow);
        } else {
        copy_row(*R, prow);
        }
    }
    return 1;
    }
}
