Poj 1753 flip game Enumeration

BFS search + bit operations speed up .. Enumerate each status and perform up, left, down, and right operations ..
When the State is 0 xFFFF or 0, it indicates that all are black or white...

If a status is not accessed, the system enters the queue and marks it as accessed ..

View code

#include <iostream>#include <cstdlib>#include <stdlib.h>#include <string.h>#include <stdio.h>#include <queue>using namespace std;char mp[100];int visit[76000];struct node{  int state;// state value  int num; // flip num }p;void bfs( ){   int flag = 0;  queue<node>q;  q.push(p);  visit[p.state] = 1;  while( !q.empty() )  {     p = q.front();     q.pop( );     node qq;     qq.state = p.state;     for( int i = 0; i < 16; i++)     {        p.state = qq.state;        p.state = p.state ^ ( 1 << i );        // up        if( i >= 4 )           p.state = p.state ^ ( 1 << ( i -4 ) );        // down        if( i <= 11 )           p.state = p.state ^ ( 1 << ( i + 4 ) );         // left        if( i % 4 != 0 )          p.state = p.state ^ ( 1 << ( i - 1 ));       //right        if ( (i + 1) % 4 != 0 )      p.state = p.state ^ ( 1 << ( i + 1 ) );                 if( p.state == 0xffff || p.state == 0 )        {                 flag = 1;              cout<<p.num +  1 << endl;              return;         }        if( visit[p.state] == 0 )        {            node temp;            temp.num = p.num + 1;            temp.state = p.state;            visit[p.state] = 1;            q.push(temp);        }   } } if( !flag )   puts("Impossible");}int main( ){    memset(visit, 0, sizeof(visit));    p.num = 0, p.state = 0;    for( int i = 0; i < 16;i++)    {       cin>>mp[i];         }     for( int i = 0; i < 16; i++)    {      if( mp[i] == 'b' )    p.state += (1<<i);    }    if( p.state == 0xffff || p.state == 0 )   {        puts("0");   }    else   {     bfs( );   }  return 0;}