cmpsc330hw5/strategic_player1.cxx

#include "strategic_player1.h"

extern "C" IPlayer *PlayerFactory() {
    return new StrategicPlayer1();
}

using namespace std;

string StrategicPlayer1::PlayerInfo() {
    return "Sandipsinh Rathod (sdr5549@psu.edu), Sapan Shah (scs6041@psu.edu)";
}

void StrategicPlayer1::Init(int board_rows, int board_cols, char box_type, char line_type) {
    this->box_name = box_type;
    this->name = line_type;

    int blank_line_count = 0;
    board.AllocateBoard(board_rows, board_cols, blank_line_count);
}

void StrategicPlayer1::Close() {
    board.FreeBoard();
}

void StrategicPlayer1::EventAddLine(char bar, const Loc &loc) {
    board(loc) = bar;
}

void StrategicPlayer1::EventAddBox(char box, const Loc &loc) {
    board(loc) = box;
}

Loc StrategicPlayer1::SelectLineLocation() {
    vector<Loc> empty_lines;
    ListEmptyLines(empty_lines);

    // Step 1: Look for a move to complete a box
    Loc move = FindBoxCompletingMove();
    if (move.row != -1) {
        return move;
    }

    // Step 2: Force opponent into bad moves
    move = ForceOpponentMistake(empty_lines);
    if (move.row != -1) {
        return move;
    }

    // Step 3: Fall back to the optimal move
    return FindOptimalMove();
}

StrategicPlayer1::~StrategicPlayer1() {
    Close();
}

Loc StrategicPlayer1::FindBoxCompletingMove() {
    vector<Loc> empty_lines;
    ListEmptyLines(empty_lines);

    for (const Loc &loc: empty_lines) {
        int row = loc.row, col = loc.col;
        if (DoesMoveCompleteBox(row, col)) {
            return loc;
        }
    }

    return Loc(-1, -1);
}

bool StrategicPlayer1::DoesMoveCompleteBox(int row, int col) {
    if (!(row & 1) && col & 1) {
        return (CountBoxLines(row - 1, col) == 3 || CountBoxLines(row + 1, col) == 3);
    } else if (row & 1 && !(col & 1)) {
        return (CountBoxLines(row, col - 1) == 3 || CountBoxLines(row, col + 1) == 3);
    }
    return false;
}

Loc StrategicPlayer1::ForceOpponentMistake(const vector<Loc> &empty_lines) {
    Loc best_move(-1, -1);

    for (const Loc &loc: empty_lines) {
        if (!DoesMoveCreateChain(loc.row, loc.col)) {
            return loc;
        }
    }

    return best_move;
}

Loc StrategicPlayer1::FindOptimalMove() {
    vector<Loc> empty_lines;
    ListEmptyLines(empty_lines);

    int min_cost = numeric_limits<int>::max();
    Loc best_move(-1, -1);

    for (const Loc &loc: empty_lines) {
        int cost = EvaluateMoveCost(loc.row, loc.col);
        if (cost < min_cost) {
            min_cost = cost;
            best_move = loc;
        }
    }

    return best_move;
}

bool StrategicPlayer1::DoesMoveCreateChain(int row, int col) {
    board(row, col) = name;

    bool creates_chain = false;

    if (!(row & 1) && col & 1) {
        if (CountBoxLines(row - 1, col) == 2 || CountBoxLines(row + 1, col) == 2) {
            creates_chain = true;
        }
    } else if (row & 1 && !(col & 1)) {
        if (CountBoxLines(row, col - 1) == 2 || CountBoxLines(row, col + 1) == 2) {
            creates_chain = true;
        }
    }

    board(row, col) = ' ';
    return creates_chain;
}

int StrategicPlayer1::EvaluateMoveCost(int row, int col) {
    int cost = 0;

    if (!(row & 1) && col & 1) { // Horizontal line
        cost += CountBoxLines(row - 1, col);
        cost += CountBoxLines(row + 1, col);
    } else if (row & 1 && !(col & 1)) { // Vertical line
        cost += CountBoxLines(row, col - 1);
        cost += CountBoxLines(row, col + 1);
    }

    return cost;
}

int StrategicPlayer1::CountBoxLines(int row, int col) {
    if (row < 0 || row >= board.GetRows() || col < 0 || col >= board.GetCols()) {
        return 0;
    }

    int count = 0;
    if (board(row - 1, col) != ' ') count++; // Top
    if (board(row + 1, col) != ' ') count++; // Bottom
    if (board(row, col - 1) != ' ') count++; // Left
    if (board(row, col + 1) != ' ') count++; // Right

    return count;
}

void StrategicPlayer1::ListEmptyLines(vector<Loc> &empty_lines) {
    for (int r = 0; r < board.GetRows(); r++) {
        for (int c = 0; c < board.GetCols(); c++) {
            Loc loc(r, c);
            if (loc.IsLineLocation() && board(r, c) == ' ') {
                empty_lines.push_back(loc);
            }
        }
    }
}