write a description for this program( please introduce the topic and applications, advantages / disadvantages)

#include

#include

#include

#include

#include

class p15 {

public :

void play() {

bool p = true;

std::string a;

while( p ) {

createBrd();

while( !isDone() ) { drawBrd();getMove(); }

drawBrd();

std::cout << " Congratulations! Play again (Y/N)?";

std::cin >> a; if( a != "Y" && a != "y" ) break;

}

}

private:

void createBrd() {

int i = 1; std::vector v;

for( ; i < 16; i++ ) { brd[i - 1] = i; }

brd[15] = 0; x = y = 3;

for( i = 0; i < 1000; i++ ) {

getCandidates( v );

move( v[rand() % v.size()] );

v.clear();

}

}

void move( int d ) {

int t = x + y * 4;

switch( d ) {

case 1: y--; break;

case 2: x++; break;

case 4: y++; break;

case 8: x--;

}

brd[t] = brd[x + y * 4];

brd[x + y * 4] = 0;

}

void getCandidates( std::vector& v ) {

if( x < 3 ) v.push_back( 2 ); if( x > 0 ) v.push_back( 8 );

if( y < 3 ) v.push_back( 4 ); if( y > 0 ) v.push_back( 1 );

}

void drawBrd() {

int r; std::cout << " ";

for( int y = 0; y < 4; y++ ) {

std::cout << "+----+----+----+----+ ";

for( int x = 0; x < 4; x++ ) {

r = brd[x + y * 4];

std::cout << "| ";

if( r < 10 ) std::cout << " ";

if( !r ) std::cout << " ";

else std::cout << r << " ";

}

std::cout << "| ";

}

std::cout << "+----+----+----+----+ ";

}

void getMove() {

std::vector v; getCandidates( v );

std::vector p; getTiles( p, v ); unsigned int i;

while( true ) {

std::cout << " Possible moves: ";

for( i = 0; i < p.size(); i++ ) std::cout << p[i] << " ";

int z; std::cin >> z;

for( i = 0; i < p.size(); i++ )

if( z == p[i] ) { move( v[i] ); return; }

}

}

void getTiles( std::vector& p, std::vector& v ) {

for( unsigned int t = 0; t < v.size(); t++ ) {

int xx = x, yy = y;

switch( v[t] ) {

case 1: yy--; break;

case 2: xx++; break;

case 4: yy++; break;

case 8: xx--;

}

p.push_back( brd[xx + yy * 4] );

}

}

bool isDone() {

for( int i = 0; i < 15; i++ ) {

if( brd[i] != i + 1 ) return false;

}

return true;

}

int brd[16], x, y;

};

int main( int argc, char* argv[] ) {

srand( ( unsigned )time( 0 ) );

p15 p; p.play(); return 0;

}