bool reduceRoute(solution &sol, const problem& input){
if(sol.routes.size() <= 1) return false;
unsigned int before = sol.routes.size();
// find route with highest (distance / # of customers).
list<route>::iterator minR;
double dis = 0;
for(list<route>::iterator it = sol.routes.begin(); it != sol.routes.end(); it++){
double p = it->distance / it->visits.size();
if(p > dis){
minR = it;
dis = p;
}
}
// remove this shortest route
route shortest = (*minR);
sol.routes.erase(minR);
for(list<int>::iterator cus = shortest.visits.begin(); cus != shortest.visits.end();){
solution min = sol;
for(int tryCount = 0; tryCount < input.getNumCusto(); tryCount++){
solution temp = min;
list<route>::iterator r = temp.routes.begin();
advance(r, rand() % temp.routes.size() );
list<int>::iterator ins = r->visits.begin();
advance(ins, r->visits.size());
r->visits.insert(ins, *cus);
r->modified = true;
temp.fitness(input);
if(temp.totalDistance < min.totalDistance){
min = temp;
}
}
if(min.totalDistance < sol.totalDistance){
cus = shortest.visits.erase(cus);
shortest.modified = true;
sol = min;
}else{
cus++;
}
}
// append a new route with customers can't be inserted.
if( !shortest.visits.empty() ){
sol.routes.push_front(shortest);
}
return (sol.routes.size() < before);
}
void mutation(solution &sol, const problem& input){
int tryCount = 0;
while(tryCount < input.getNumCusto() ){
solution test = sol;
// randomly select two routes
list<route>::iterator routeA = test.routes.begin();
advance(routeA, rand() % test.routes.size() );
list<route>::iterator routeB = test.routes.begin();
advance(routeB, rand() % test.routes.size() );
// # of feasible route BEFORE the reinsertion
int beforeFeasibleCount = 0;
if(routeA->feasible) beforeFeasibleCount++;
if(routeB->feasible) beforeFeasibleCount++;
// randomly select two positions
list<int>::iterator cusA = routeA->visits.begin();
advance(cusA, rand() % routeA->visits.size() );
list<int>::iterator cusB = routeB->visits.begin();
advance(cusB, rand() % routeB->visits.size() );
routeB->visits.insert(cusB, *cusA);
routeB->modified = true;
routeA->visits.erase(cusA);
routeA->modified = true;
bool reduce = false;
if( routeA->visits.empty() ){
test.routes.erase(routeA);
reduce = true;
}
test.fitness(input);
// # of feasible route AFTER the reinsertion
int afterFeasibleCount = 0;
if(reduce || routeA->feasible) afterFeasibleCount++;
if(routeB->feasible) afterFeasibleCount++;
if(afterFeasibleCount >= beforeFeasibleCount) sol = test;
tryCount++;
}
}
void solution::random(int maxRoutes, const problem& input){
clear();
vector< vector<int> > newRoutes;
newRoutes.resize(maxRoutes);
for(int id = 1; id <= input.getNumCusto(); ++id){
newRoutes[ rand() % maxRoutes ].push_back(id);
}
for(int i = 0; i < maxRoutes; ++i){
if(newRoutes[i].size() > 0){
// insert customers according to time windows' position
vector<int> sorted;
sorted.reserve(newRoutes[i].size());
for(unsigned int j = 0; j < sorted.capacity(); ++j){
int minStart = input[0].end, minEnd = input[0].end, id;
for(unsigned int k = 0; k < newRoutes[i].size(); ++k){
if(input[ newRoutes[i][k] ].end < minEnd){
minEnd = input[ newRoutes[i][k] ].end;
minStart = input[ newRoutes[i][k] ].start;
id = k;
}else if(input[ newRoutes[i][k] ].end == minEnd && input[ newRoutes[i][k] ].start < minStart ){
minStart = input[ newRoutes[i][k] ].start;
id = k;
}
}
sorted.push_back(newRoutes[i][id]);
newRoutes[i].erase(newRoutes[i].begin() + id);
}
route newRoute;
newRoute.visits = list<int>(sorted.begin(), sorted.end());
routes.push_back(newRoute);
}
}
fitness(input);
}