//getNextStep determines the step the computer will make given the current status
//of the board and the difficulty level
public static State getNextStep(State s, int diff)
{
List<State> possible = new List<State>();
List<Tree> tree = new List<Tree>();
for (int i = 8; i < 16; i++)
{
s.addStep(i, possible, false);
}
foreach (State st in possible)
{
Tree fresh = new Tree(st);
tree.Add(fresh);
}
//for different difficulty level(lvl3 is disabled due to memory constraint)
switch (diff)
{
case 1:
foreach (Tree t in tree)
{
t.populate(2);
}
break;
case 2:
foreach (Tree t in tree)
{
t.populate(4);
}
break;
case 3:
foreach (Tree t in tree)
{
t.populate(6);
}
break;
default:
break;
}
foreach (Tree t in tree)
{
t.calc();
}
int max = -2000;
int refer = 0;
int num = 0;
int c = 0;
foreach (Tree t in tree)
{
if (t.value > max)
{
max = t.value;
refer = num;
}
if (t.value == max)
{
c++;
}
num++;
}
if (c != 1)
{
num = 0;
foreach (Tree t in tree)
{
if(t.value == max)
{
t.state.eval();
if (t.state.value > max)
{
max = t.state.value;
refer = num;
}
}
num++;
}
}
if (possible.Count == 0) return null;
//find the most yielding step and return its state
return possible[refer];
}
public bool checkLose(int player)
{
bool lose = true;
foreach (Piece p in pcs)
{
if (p.owner == player) lose = false;
}
State news = new State();
for (int i = 0; i < 16; i++)
{
int owner = pcs[i].owner;
if (owner == 0)
{
news.state[i, 0] = -1;
news.state[i, 1] = -1;
news.state[i, 2] = -1;
}
else
{
news.state[i, 0] = pcs[i].x;
news.state[i, 1] = pcs[i].y;
news.state[i, 2] = pcs[i].king ? 1 : 0;
}
}
List<State> check = new List<State>();
for (int i = (player - 1) * 8; i < (player - 1) * 8 + 8; i++)
{
news.addStep(i, check, false);
}
if (check.Count == 0)
{
lose = true;
}
return lose;
}
//addStep adds all the possible states that can be derived from the current state when moving the piece i
//into a predefined List dest
public void addStep(int i, List<State> dest, bool done) {
//done is if the piece had made a move in this turn, done will prevent the piece from making a non-eating move
bool yellow = i < 8;
if (state[i, 0] == -1) return; //invalid piece
if(state[i, 2] == 0 && yellow) { //yellow player moving yellow piece
int locr = find(state[i, 0] + 1, state[i, 1] + 1); //the two pieces that a non-king piece can move to without eating other pieces
int locl = find(state[i, 0] - 1, state[i, 1] + 1);
//if the right spot is empty
if(locr == -1 && !done) {
State next = new State(this);
next.state[i, 0]++;
next.state[i, 1]++;
if(next.state[i, 1] == 7) next.state[i, 2] = 1;
dest.Add(next);
}else if(locr > 7) { //if the piece next to it is black
int endp = find(state[i, 0] + 2, state[i, 1] + 2);
if(endp == -1) { //if the destination is empty
State next = new State(this);
next.state[locr, 0] = -1;
next.state[locr, 1] = -1;
next.state[i, 0] += 2;
next.state[i, 1] += 2;
next.jumped = new List<coor>();
foreach (coor c in this.jumped)
{
next.jumped.Add(c);
}
next.jumped.Add(new coor(state[i, 0] + 2, state[i, 1] + 2));
if(next.state[i, 1] == 7) next.state[i, 2] = 1;
dest.Add(next);
next.addStep(i, dest, true);
}
}
//if the left spot is empty
if(locl == -1 && !done) {
State next = new State(this);
next.state[i, 0]--;
next.state[i, 1]++;
if(next.state[i, 1] == 7) next.state[i, 2] = 1;
dest.Add(next);
//if the left spot is black
}else if(locl > 7) {
int endp = find(state[i, 0] - 2, state[i, 1] + 2);
if(endp == -1) {
State next = new State(this);
next.state[locl, 0] = -1;
next.state[locl, 1] = -1;
next.state[i, 0] -= 2;
next.state[i, 1] += 2;
next.jumped = new List<coor>();
foreach (coor c in this.jumped)
{
next.jumped.Add(c);
}
next.jumped.Add(new coor(state[i, 0] - 2, state[i, 1] + 2));
if(next.state[i, 1] == 7) next.state[i, 2] = 1;
dest.Add(next);
next.addStep(i, dest, true);
}
}
//when it's black's turn
}else if(state[i, 2] == 0 && !yellow) {
int locr = find(state[i, 0] + 1, state[i, 1] - 1);
int locl = find(state[i, 0] - 1, state[i, 1] - 1);
if(locr == -1 && !done) {
State next = new State(this);
next.state[i, 0]++;
next.state[i, 1]--;
if (next.state[i, 1] == 0) next.state[i, 2] = 1;
dest.Add(next);
}else if(locr <= 7 && locr != -1) {
int endp = find(state[i, 0] + 2, state[i, 1] - 2);
if(endp == -1) {
State next = new State(this);
next.state[locr, 0] = -1;
next.state[locr, 1] = -1;
next.state[i, 0] += 2;
next.state[i, 1] -= 2;
next.jumped = new List<coor>();
foreach (coor c in this.jumped)
{
next.jumped.Add(c);
}
next.jumped.Add(new coor(state[i, 0] + 2, state[i, 1] - 2));
if(next.state[i, 1] == 0) next.state[i, 2] = 1;
dest.Add(next);
next.addStep(i, dest, true);
}
}
//left empty
if(locl == -1 && !done) {
State next = new State(this);
next.state[i, 0]--;
next.state[i, 1]--;
if(next.state[i, 1] == 0) next.state[i, 2] = 1;
dest.Add(next);
}
//left yellow
else if (locl <= 7 && locl != -1)
{
int endp = find(state[i, 0] - 2, state[i, 1] - 2);
if(endp == -1) {
State next = new State(this);
next.state[locl, 0] = -1;
next.state[locl, 1] = -1;
next.state[i, 0] -= 2;
next.state[i, 1] -= 2;
next.jumped = new List<coor>();
foreach (coor c in this.jumped)
{
next.jumped.Add(c);
}
next.jumped.Add(new coor(state[i, 0] - 2, state[i, 1] - 2));
if(next.state[i, 1] == 0) next.state[i, 2] = 1;
dest.Add(next);
next.addStep(i, dest, true);
}
}
//if piece is king
}else if(state[i, 2] == 1) {
int[] loc = new int[4];
loc[0] = find(state[i, 0] + 1, state[i, 1] - 1);
loc[1] = find(state[i, 0] - 1, state[i, 1] - 1);
loc[3] = find(state[i, 0] - 1, state[i, 1] + 1);
loc[2] = find(state[i, 0] + 1, state[i, 1] + 1);
for(int j = 0; j < 4; j++) {
int x = j % 2 == 0 ? 1 : -1;
int y = j < 2 ? -1 : 1;
if(loc[j] == -1 && !done) {
State next = new State(this);
next.state[i, 0] += x;
next.state[i, 1] += y;
dest.Add(next);
}else if((loc[j] > 7 && yellow) || (loc[j] <= 7 && !yellow && loc[j] != -1)) {
int endp = find(state[i, 0] + 2 * x, state[i, 1] + 2 * y);
if(endp == -1) {
State next = new State(this);
next.state[loc[j], 0] = -1;
next.state[loc[j], 1] = -1;
next.state[i, 0] += 2 * x;
next.state[i, 1] += 2 * y;
next.jumped = new List<coor>();
foreach (coor c in this.jumped)
{
next.jumped.Add(c);
}
next.jumped.Add(new coor(state[i, 0] + 2 * x, state[i, 1] + 2 * y));
dest.Add(next);
next.addStep(i, dest, true);
}
}
}
}
}