int
Munkres::step4(void) {
int rows = matrix.rows();
int cols = matrix.columns();
std::list<std::pair<int,int> > seq;
// use saverow, savecol from step 3.
std::pair<int,int> z0(saverow, savecol);
std::pair<int,int> z1(-1,-1);
std::pair<int,int> z2n(-1,-1);
seq.insert(seq.end(), z0);
int row, col = savecol;
/*
Increment Set of Starred Zeros
1. Construct the ``alternating sequence'' of primed and starred zeros:
Z0 : Unpaired Z' from Step 4.2
Z1 : The Z* in the column of Z0
Z[2N] : The Z' in the row of Z[2N-1], if such a zero exists
Z[2N+1] : The Z* in the column of Z[2N]
The sequence eventually terminates with an unpaired Z' = Z[2N] for some N.
*/
bool madepair;
do {
madepair = false;
for ( row = 0 ; row < rows ; row++ )
if ( mask_matrix(row,col) == STAR ) {
z1.first = row;
z1.second = col;
if ( pair_in_list(z1, seq) )
continue;
madepair = true;
seq.insert(seq.end(), z1);
break;
}
if ( !madepair )
break;
madepair = false;
for ( col = 0 ; col < cols ; col++ )
if ( mask_matrix(row,col) == PRIME ) {
z2n.first = row;
z2n.second = col;
if ( pair_in_list(z2n, seq) )
continue;
madepair = true;
seq.insert(seq.end(), z2n);
break;
}
} while ( madepair );
for ( std::list<std::pair<int,int> >::iterator i = seq.begin() ;
i != seq.end() ;
i++ ) {
// 2. Unstar each starred zero of the sequence.
if ( mask_matrix(i->first,i->second) == STAR )
mask_matrix(i->first,i->second) = NORMAL;
// 3. Star each primed zero of the sequence,
// thus increasing the number of starred zeros by one.
if ( mask_matrix(i->first,i->second) == PRIME )
mask_matrix(i->first,i->second) = STAR;
}
// 4. Erase all primes, uncover all columns and rows,
for ( int row = 0 ; row < mask_matrix.rows() ; row++ )
for ( int col = 0 ; col < mask_matrix.columns() ; col++ )
if ( mask_matrix(row,col) == PRIME )
mask_matrix(row,col) = NORMAL;
for ( int i = 0 ; i < rows ; i++ ) {
row_mask[i] = false;
}
for ( int i = 0 ; i < cols ; i++ ) {
col_mask[i] = false;
}
// and return to Step 2.
return 2;
}
/*!
Increment Set of Starred Zeros
1. Construct the ``alternating sequence'' of primed and starred zeros:
Z0 : Unpaired Z' from Step 4.2
Z1 : The Z* in the column of Z0
Z[2N] : The Z' in the row of Z[2N-1], if such a zero exists
Z[2N+1] : The Z* in the column of Z[2N]
The sequence eventually terminates with an unpaired Z' = Z[2N] for some N.
*/
int Munkres::step4(void)
{
std::list<std::pair<int,int> > seq;
// use saverow, savecol from step 3.
std::pair<int,int> z0(saverow, savecol);
std::pair<int,int> z1(-1,-1);
std::pair<int,int> z2n(-1,-1);
seq.insert(seq.end(), z0);
unsigned row, col = savecol;
bool madepair;
do {
madepair = false;
for ( row = 0 ; row < matrix.rows() ; row++ )
if ( mask_matrix(row,col) == Z_STAR ) {
z1.first = row;
z1.second = col;
if ( pair_in_list(z1, seq) )
continue;
madepair = true;
seq.insert(seq.end(), z1);
break;
}
if ( !madepair )
break;
madepair = false;
for ( col = 0 ; col < matrix.columns() ; col++ )
if ( mask_matrix(row,col) == Z_PRIME ) {
z2n.first = row;
z2n.second = col;
if ( pair_in_list(z2n, seq) )
continue;
madepair = true;
seq.insert(seq.end(), z2n);
break;
}
} while ( madepair );
for ( std::list<std::pair<int,int> >::iterator i = seq.begin() ;
i != seq.end() ;
i++ ) {
// 2. Unstar each starred zero of the sequence.
if ( mask_matrix(i->first,i->second) == Z_STAR )
mask_matrix(i->first,i->second) = Z_NORMAL;
// 3. Star each primed zero of the sequence,
// thus increasing the number of starred zeros by one.
if ( mask_matrix(i->first,i->second) == Z_PRIME )
mask_matrix(i->first,i->second) = Z_STAR;
}
// 4. Erase all primes, uncover all columns and rows,
for ( unsigned row = 0 ; row < mask_matrix.rows() ; row++ )
for ( unsigned col = 0 ; col < mask_matrix.columns() ; col++ )
if ( mask_matrix(row,col) == Z_PRIME )
mask_matrix(row,col) = Z_NORMAL;
for ( unsigned i = 0 ; i < matrix.rows() ; i++ ) {
row_mask[i] = false;
}
for ( unsigned i = 0 ; i < matrix.columns() ; i++ ) {
col_mask[i] = false;
}
// and return to Step 2.
return 2;
}
