#include??? < stdio.h > ?

#define ???N???100?
#define ???OPEN???1?
#define ???CLOSED???0?

void ???switch_door( int ??? * door)?
{?
???????? if ( * door??? == ???OPEN)?
???????????????? * door??? = ???CLOSED;?
???????? else ?
???????????????? * door??? = ???OPEN;?
} ?

int ???main( void )?
{?
???????? int ???door[N??? + ??? 1 ];??? // ???waste???a???door?
???????? int ???person;?
???????? int ???i;?

???????? for (i??? = ??? 1 ;???i??? <= ???N;???i ++ )?
????????????????door[i]??? = ???OPEN;??? // ???all???doors???are???open???at???first?

???????? for (i??? = ??? 1 ;???i??? <= ???N;???i ++ )?
???????????????? for (person??? = ??? 1 ;???person??? <= ???N;???person ++ )??? // ???person???pass???through???the???door?
???????????????????????? if (i??? % ???person??? == ??? 0 )?
????????????????????????????????switch_door( & door[i]);?

???????? for (i??? = ??? 1 ;???i??? <= ???N;???i ++ )?
????????????????printf(? " door???%d:???%s\n? " ,???i,???door[i]??? ? ??? " Open? " ???:??? " Closed? " );?

???????? return ??? 0 ;?
} ?

帖上代碼：?
#include??? < iostream > ?
#include??? < cmath > ?
using ??? namespace ???std;?

int ???main()?
{?
???????? int ???k;?
???????? for ( int ???i??? = ??? 1 ;???i??? <= 100 ;???i ++ )?
???????? {?
????????cout??? < ? < ??? " Door??? " ??? < ? < ???i???;?
????????k??? = ??? int (sqrt(i));?
???????? if (k * k??? == ???i)?
????????cout??? < ? < ??? " :???Closed? " ;?
???????? else ?
????????cout??? < ? < ??? " :???Open? " ;?
????????cout??? < ? < ???endl;?
????????} ?
return ??? 0 ;?
} ?
當然，這是利用了人數與門數是相等的情況。如果個數不同的話，還是按照一樓的來。