// This function does the actual solving.
void solvePuzzle(PuzzleState *start, BagOfPuzzleStates &active, PredDict &seen, vector<PuzzleState*> &solution) {
PuzzleState *state;
PuzzleState *temp;
active.put_in(start); // Must explore the successors of the start state.
seen.add(start,NULL); // We've seen this state. It has no predecessor.
int foo=0;
while (!active.is_empty()) {
// Loop Invariants:
// 'seen' contains the set of puzzle states that we know how to reach.
// 'active' contains the set of puzzle states that we know how to reach,
// and whose successors we might not have explored yet.
foo++;
if (foo % 1000 == 0) cout << foo << endl;
state = active.take_out();
// Note: Do not delete this, as this PuzzleState is also in 'seen'
// The following two lines are handy for debugging, or seeing what
// the algorithm is doing.
// 221 STUDENTS: Comment these out when you want the program to
// run at full speed!
//cout << "Exploring State: \n";
//state->print(cout);
//usleep(100000); // Pause for some microseconds, to let human read output
if (state->isSolution()) {
// Found a solution!
cout << "Found solution! \n";
state->print(cout);
// Follow predecessors to construct path to solution.
temp = state;
while (temp!=NULL) {
solution.push_back(temp);
// Guaranteed to succeed, because these states must have been
// added to dictionary already.
seen.find(temp,temp);
}
return;
}
vector<PuzzleState*> nextMoves = state->getSuccessors();
for (unsigned int i=0; i < nextMoves.size(); i++) {
if (!seen.find(nextMoves[i], temp)) {
// Never seen this state before. Add it to 'seen' and 'active'
active.put_in(nextMoves[i]);
seen.add(nextMoves[i], state);
} else {
delete nextMoves[i];
}
}
}
// Ran out of states to explore. No solution!
solution.clear();
return;
}
// This function does the actual solving.
void solvePuzzle(PuzzleState *start, TodoList<PuzzleState*> &active, PredDict<PuzzleState*> &seen, vector<PuzzleState*> &solution) {
PuzzleState *state;
PuzzleState *temp;
active.add(start); // Must explore the successors of the start state.
seen.add(start,NULL); // We've seen this state. It has no predecessor.
while (!active.is_empty()) {
// Loop Invariants:
// 'seen' contains the set of puzzle states that we know how to reach.
// 'active' contains the set of puzzle states that we know how to reach,
// and whose successors we might not have explored yet.
state = active.remove();
// Note: Do not delete this, as this PuzzleState is also in 'seen'
// uncomment the next two lines for debugging, if you'd like!
// cout << "Exploring State: \n";
// state->print(cout);
// cin.get();
if (state->isSolution()) {
// Found a solution!
cout << "Found solution! \n";
state->print(cout);
// Follow predecessors to construct path to solution.
temp = state;
while (temp!=NULL) {
solution.push_back(temp);
// Guaranteed to succeed, because these states must have been
// added to dictionary already.
seen.find(temp,temp);
}
return;
}
vector<PuzzleState*> nextMoves = state->getSuccessors();
for (unsigned int i=0; i < nextMoves.size(); i++) {
if (!seen.find(nextMoves[i], temp)) {
// Never seen this state before. Add it to 'seen' and 'active'
active.add(nextMoves[i]);
seen.add(nextMoves[i], state);
}
else {
// We're not using this duplicate state;
// so, we should delete it.
delete nextMoves[i];
}
}
}
// Ran out of states to explore. No solution!
cout << "No solution!" << endl;
solution.clear();
return;
}
// This function does the actual solving.
void solveMaze(MazeState *start, BagOfMazeStates &active, PredDict &seen) {
MazeState *state;
MazeState *temp;
active.add(start); // Must explore the successors of the start state.
seen.add(start,NULL); // We've seen this state. It has no predecessor.
while (!active.is_empty()) {
// Loop Invariants:
// 'seen' contains the set of maze states that we know how to reach.
// 'active' contains the set of maze states that we know how to reach,
// and from which there may be new states we haven't explored yet.
state = active.remove();
// Note: Don't delete state when done, as this MazeState is also in seen
// The following two lines are handy for debugging, or seeing what
// the algorithm is doing.
// 221 STUDENTS: Comment these out when you want the program to
// run at full speed!
//cout << "Exploring State: \n";
//state->print(cout);
//usleep(20000); // Pause for some microseconds, to let human read output
if (state->isSolution()) {
// Found a solution!
cout << "***** Found a solution!!!!! ***** \n";
int temp; // Throwaway variable to call recursive printTraceTo
printTraceTo(state, seen, temp);
return;
}
vector<MazeState*> nextMoves = state->getSuccessors();
for (unsigned int i=0; i < nextMoves.size(); i++) {
if (!seen.find(nextMoves[i], temp)) {
// Never seen this state before. Add it to 'seen' and 'active'
active.add(nextMoves[i]);
seen.add(nextMoves[i], state);
} else {
delete nextMoves[i];
}
}
}
// Ran out of states to explore. No solution!
cout << "***** No Solution Exists!!! *****\n";
return;
}
// Simple recursive function to print out a sequence of states from
// the start state to goal.
// length returns how many steps there were in the path to goal.
void printTraceTo(MazeState *goal, PredDict &seen, int &length) {
// Should not be called with NULL
if (goal==NULL) {
cerr << "Error: Do not call printSolution without a goal.\n";
return;
}
// Find the state that we used to get to goal.
MazeState *predecessor;
seen.find(goal,predecessor);
if (predecessor==NULL) {
// Base Case: If predecessor is NULL, then goal is the starting state.
length = 0;
cout << "Starting from this state:\n";
goal->print(cout);
} else {
// Recursive Case: Print solution to predecessor, then one step to goal.
printTraceTo(predecessor, seen, length);
length++;
cout << "Step " << length << " leads to...\n";
goal->print(cout);
}
}
