// remove (one) edge between node u,v
// note that when the node becomes standalone, also rip its color
bool ConstraintGraph::remove_edge(const GNode &u,const GNode &v){
GEdge &uv = access_edge(u,v);
GEdge &vu = access_edge(v,u);
GNode &unode = access_node(u);
GNode &vnode = access_node(v);
assert( uv.count == vu.count );
// edge not exist,
if( uv.count == 0 ) return false;
uv.count--;
if( uv.count == 0 ) uv.type = NOEDGE;
unode.ecount--;
if( unode.ecount == 0 ) erase_color(u);
vu.count--; // symmetric
if( vu.count == 0 ) vu.type = NOEDGE;
vnode.ecount--;
if( vnode.ecount == 0 ) erase_color(v);
return true;
}
void rbtree::remove(node *n) noexcept {
node * child,*parent;
unsigned color;
if (!n->_left) {
child = n->_right;
}
else if (!n->_right) {
child = n->_left;
}
else {
node *old = n, *left;
n = n->_right;
while ((left = n->_left) != 0) {
n = left;
}
child = n->_right;
parent = n->parent();
color = n->color();
if (child) {
child->parent(parent);
}
if (parent == old) {
parent->_right = child;
parent = n;
}
else {
parent->_left = child;
}
n->_parent_color = old->_parent_color;
n->_right = old->_right;
n->_left = old->_left;
if (old->parent()) {
if (old->parent()->_left == old) {
old->parent()->_left = n;
}
else {
old->parent()->_right = n;
}
}
else {
_root = n;
}
old->_left->parent(n);
if (old->_right) {
old->_right->parent(n);
}
goto color;
}
parent = n->parent();
color = n->color();
if (child) {
child->parent(parent);
}
if (parent) {
if (parent->_left == n) {
parent->_left = child;
}
else {
parent->_right = child;
}
}
else {
_root = child;
}
color:
if (color == GV_RB_BLACK) {
erase_color(child, parent);
}
}
