Task: 15 puzzle game
C: 
#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define N 4
#define M 4
enum Move{UP,DOWN,LEFT,RIGHT};int hR;int hC;int cc[N][M];const int nS=100;int
update(enum Move m){const int dx[]={0,0,-1,1};const int dy[]={-1,1,0,0};int i=hR
+dy[m];int j=hC+dx[m];if(i>= 0&&i<N&&j>=0&&j<M){cc[hR][hC]=cc[i][j];cc[i][j]=0;
hR=i;hC=j;return 1;}return 0;}void setup(void){int i,j,k;for(i=0;i<N;i++)for(j=0
;j<M;j++)cc[i][j]=i*M+j+1;cc[N-1][M-1]=0;hR=N-1;hC=M-1;k=0;while(k<nS)k+=update(
(enum Move)(rand()%4));}int isEnd(void){int i,j; int k=1;for(i=0;i<N;i++)for(j=0
;j<M;j++)if((k<N*M)&&(cc[i][j]!=k++))return 0;return 1;}void show(){int i,j;
putchar('\n');for(i=0;i<N;i++)for(j=0;j<M;j++){if(cc[i][j])printf(j!=M-1?" %2d "
:" %2d \n",cc[i][j]);else printf(j!=M-1?" %2s ":" %2s \n", "");}putchar('\n');}
void disp(char* s){printf("\n%s\n", s);}enum Move get(void){int c;for(;;){printf
("%s","enter u/d/l/r : ");c=getchar();while(getchar()!='\n');switch(c){case 27:
exit(0);case'd':return UP;case'u':return DOWN;case'r':return LEFT;case'l':return
RIGHT;}}}void pause(void){getchar();}int main(void){srand((unsigned)time(NULL));
do setup();while(isEnd());show();while(!isEnd()){update(get());show();}disp(
"You win"); pause();return 0;}

Java: package fifteenpuzzle;

import java.awt.*;
import java.awt.event.*;
import java.util.Random;
import javax.swing.*;

class FifteenPuzzle extends JPanel {

    private final int side = 4;
    private final int numTiles = side * side - 1;

    private final Random rand = new Random();
    private final int[] tiles = new int[numTiles + 1];
    private final int tileSize;
    private int blankPos;
    private final int margin;
    private final int gridSize;
    private boolean gameOver;

    private FifteenPuzzle() {
        final int dim = 640;

        margin = 80;
        tileSize = (dim - 2 * margin) / side;
        gridSize = tileSize * side;

        setPreferredSize(new Dimension(dim, dim + margin));
        setBackground(Color.WHITE);
        setForeground(new Color(0x6495ED)); 
        setFont(new Font("SansSerif", Font.BOLD, 60));

        gameOver = true;

        addMouseListener(new MouseAdapter() {
            @Override
            public void mousePressed(MouseEvent e) {
                if (gameOver) {
                    newGame();

                } else {

                    int ex = e.getX() - margin;
                    int ey = e.getY() - margin;

                    if (ex < 0 || ex > gridSize || ey < 0 || ey > gridSize) {
                        return;
                    }

                    int c1 = ex / tileSize;
                    int r1 = ey / tileSize;
                    int c2 = blankPos % side;
                    int r2 = blankPos / side;

                    int clickPos = r1 * side + c1;

                    int dir = 0;
                    if (c1 == c2 && Math.abs(r1 - r2) > 0) {
                        dir = (r1 - r2) > 0 ? 4 : -4;
                        
                    } else if (r1 == r2 && Math.abs(c1 - c2) > 0) {
                        dir = (c1 - c2) > 0 ? 1 : -1;
                    }

                    if (dir != 0) {
                        do {
                            int newBlankPos = blankPos + dir;
                            tiles[blankPos] = tiles[newBlankPos];
                            blankPos = newBlankPos;
                        } while (blankPos != clickPos);
                        tiles[blankPos] = 0;
                    }
                    
                    gameOver = isSolved();
                }
                repaint();
            }
        });

        newGame();
    }

    private void newGame() {
        do {
            reset();
            shuffle();
        } while (!isSolvable());
        gameOver = false;
    }

    private void reset() {
        for (int i = 0; i < tiles.length; i++) {
            tiles[i] = (i + 1) % tiles.length;
        }
        blankPos = tiles.length - 1;
    }

    private void shuffle() {
        
        
        int n = numTiles;
        while (n > 1) {
            int r = rand.nextInt(n--);
            int tmp = tiles[r];
            tiles[r] = tiles[n];
            tiles[n] = tmp;
        }
    }

    
    private boolean isSolvable() {
        int countInversions = 0;
        for (int i = 0; i < numTiles; i++) {
            for (int j = 0; j < i; j++) {
                if (tiles[j] > tiles[i]) {
                    countInversions++;
                }
            }
        }
        return countInversions % 2 == 0;
    }

    private boolean isSolved() {
        if (tiles[tiles.length - 1] != 0) {
            return false;
        }
        for (int i = numTiles - 1; i >= 0; i--) {
            if (tiles[i] != i + 1) {
                return false;
            }
        }
        return true;
    }

    private void drawGrid(Graphics2D g) {
        for (int i = 0; i < tiles.length; i++) {
            int r = i / side;
            int c = i % side;
            int x = margin + c * tileSize;
            int y = margin + r * tileSize;

            if (tiles[i] == 0) {
                if (gameOver) {
                    g.setColor(Color.GREEN);
                    drawCenteredString(g, "\u2713", x, y);
                }
                continue;
            }

            g.setColor(getForeground());
            g.fillRoundRect(x, y, tileSize, tileSize, 25, 25);
            g.setColor(Color.blue.darker());
            g.drawRoundRect(x, y, tileSize, tileSize, 25, 25);
            g.setColor(Color.WHITE);

            drawCenteredString(g, String.valueOf(tiles[i]), x, y);
        }
    }

    private void drawStartMessage(Graphics2D g) {
        if (gameOver) {
            g.setFont(getFont().deriveFont(Font.BOLD, 18));
            g.setColor(getForeground());
            String s = "click to start a new game";
            int x = (getWidth() - g.getFontMetrics().stringWidth(s)) / 2;
            int y = getHeight() - margin;
            g.drawString(s, x, y);
        }
    }

    private void drawCenteredString(Graphics2D g, String s, int x, int y) {
        FontMetrics fm = g.getFontMetrics();
        int asc = fm.getAscent();
        int des = fm.getDescent();

        x = x + (tileSize - fm.stringWidth(s)) / 2;
        y = y + (asc + (tileSize - (asc + des)) / 2);

        g.drawString(s, x, y);
    }

    @Override
    public void paintComponent(Graphics gg) {
        super.paintComponent(gg);
        Graphics2D g = (Graphics2D) gg;
        g.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON);

        drawGrid(g);
        drawStartMessage(g);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            JFrame f = new JFrame();
            f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            f.setTitle("Fifteen Puzzle");
            f.setResizable(false);
            f.add(new FifteenPuzzle(), BorderLayout.CENTER);
            f.pack();
            f.setLocationRelativeTo(null);
            f.setVisible(true);
        });
    }
}