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HW4-EightQueen.java
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HW4-EightQueen.java
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// Author: Nian Li
import java.util.*;
import java.lang.Math;
public class EightQueen {
public static void main(String args[]) {
if (args.length != 2 && args.length != 3) {
System.out.println("Invalid Number of Input Arguments");
return;
}
int flag = Integer.valueOf(args[0]);
int option = flag / 100;
int iteration = flag % 100;
char[] board = new char[8];
int seed = -1;
int board_index = -1;
if (args.length == 2 && (option == 1 || option == 2 || option == 4)) {
board_index = 1;
} else if (args.length == 3 && (option == 3 || option == 5)) {
seed = Integer.valueOf(args[1]);
board_index = 2;
} else {
System.out.println("Invalid Number of Input Arguments");
return;
}
if (board_index == -1) return;
for (int i = 0; i < 8; i++) {
board[i] = args[board_index].charAt(i);
int pos = board[i] - '0';
if (pos < 0 || pos > 7) {
System.out.println("Invalid input: queen position(s)");
return;
}
}
State init = new State(board);
init.printState(option, iteration, seed);
}
}
class State {
char[] board;
public State(char[] arr) {
this.board = Arrays.copyOf(arr, arr.length);
}
public void printState(int option, int iteration, int seed) {
if(option == 1){
int result = findState(this.board);
System.out.println(result);
}
else if(option == 2){
int current_state = findState(this.board);
if(current_state == 0) return;
ArrayList<char[]> optimal_states = listState(this.board);
for(char[] item : optimal_states) System.out.println(item);
System.out.println(findState(optimal_states.get(0)));
}
else if(option == 3){
Random rng = new Random();
if (seed != -1) rng.setSeed(seed);
char[] temp = Arrays.copyOf(this.board, this.board.length);
int count = 0;
System.out.print("0:");
for(int i = 0; i<8; i++) System.out.print(temp[i]);
System.out.print(" " + findState(temp) + "\n");
while(findState(temp) != 0 && count < iteration) {
ArrayList<char[]> optimal_states = listState(temp);
try{
int r = rng.nextInt(optimal_states.size());
char[] move = optimal_states.get(r);
temp = move;
count++;
System.out.print(count + ":");
for(int i = 0; i<8; i++) System.out.print(temp[i]);
System.out.print(" " + findState(temp) + "\n");
}
catch(Exception e){
return;
}
}
if(findState(temp) == 0) System.out.println("Solved");
}
else if(option == 4){
int count = 1;
char[] temp = Arrays.copyOf(this.board, this.board.length);
System.out.print("0:");
for(int i = 0; i<8; i++) System.out.print(temp[i]);
System.out.print(" " + findState(temp) + "\n");
while(findState(temp) != 0 && count <= iteration){
temp = betterMove(temp);
if(temp == null){
System.out.println("Local optimum");
return;
}
System.out.print(count + ":");
for(int i = 0; i<8; i++) System.out.print(temp[i]);
System.out.print(" " + findState(temp) + "\n");
count++;
}
if(findState(temp) == 0) System.out.println("Solved");
}
else if(option == 5){
Random rng = new Random();
if (seed != -1) rng.setSeed(seed);
char[] temp = Arrays.copyOf(this.board, this.board.length);
int count = 0;
System.out.print("0:");
for(int i = 0; i<8; i++) System.out.print(temp[i]);
System.out.print(" " + findState(temp) + "\n");
while(findState(temp) != 0 && count < iteration) {
ArrayList<char[]> optimal_states = listState(temp);
try{
int index = rng.nextInt(7);
int value = rng.nextInt(7);
double prob = rng.nextDouble();
if(prob == 0) continue;
temp[index] = Character.forDigit(value, 10);
count++;
System.out.print(count + ":");
for(int i = 0; i<8; i++) System.out.print(temp[i]);
System.out.print(" " + findState(temp) + "\n");
}
catch(IllegalArgumentException e){
return;
}
}
if(findState(temp) == 0) System.out.println("Solved");
}
}
// find the state of current board
static int findState(char[] current_board){
int stateNum = 0;
for(int i=0; i<8; i++){
int check_line = 1; // check diagonal queens, increase by 1 after each column
for(int j=i+1; j<8; j++){
if(Math.abs(current_board[i]-current_board[j]) == check_line || current_board[i] == current_board[j])stateNum++;
check_line++;
}
}
return stateNum;
}
// find the optimal char array of current board
static ArrayList<char[]> listState(char[] current_board){
int current_state = findState(current_board);
ArrayList<char[]> optimal_states = new ArrayList<>();
for(int i=0; i<8; i++){ // check 8 different columns
for(int j=0; j<8; j++) // switch queen in each column to different row except the row it holds itself
{
char[] temp = Arrays.copyOf(current_board, current_board.length);
if(j == current_board[i] - '0') continue;
temp[i] = Character.forDigit(j, 10);
int stateTest = findState(temp);
if(stateTest < current_state){
current_state = stateTest;
optimal_states.clear();
optimal_states.add(temp);
}
else if(stateTest == current_state)optimal_states.add(temp);
}
}
return optimal_states;
}
// find better move
static char[] betterMove(char[] current_board){
int current_state = findState(current_board);
for(int i=0; i<8; i++){ // check 8 different columns
for(int j=0; j<8; j++) // switch queen in each column to different row except the row it holds itself
{
char[] temp = Arrays.copyOf(current_board, current_board.length);
if(j == temp[i] - '0') continue;
temp[i] = Character.forDigit(j, 10);
int stateTest = findState(temp);
if(stateTest < current_state) return temp;
}
}
return null;
}
}