placequeens.cpp

Data Abstraction & Problem Solving with C++源码

#include "Queens.h"

bool Board::placeQueens(Queen *queenPtr)
{  
    // Base case.  Trying to place Queen in
    // a non-existent column.
    if (queenPtr->getCol() >= BOARD_SIZE)
    {   delete queenPtr;
        return true;
    }

    bool isQueenPlaced = false;

    while (!isQueenPlaced && queenPtr->getRow() < BOARD_SIZE)
    {  // If the queen can be attacked, then
       // try moving it to the next row in the
       // current column.
       if (queenPtr->isUnderAttack())
           queenPtr->nextRow();
       // Else put this queen on the board and
       // try putting a new queen in the first row
       // of the next column.
       else 
       {  setQueen(queenPtr);
          Queen *newQueenPtr = new Queen(0, queenPtr->getCol() + 1);
          isQueenPlaced = placeQueens(newQueenPtr);
          // If it wasn't possible to put the new
          // Queen in the next column, backtrack
          // by deleting the new Queen and
          // removing the last Queen placed and
          // moving it down one row.
          if (!isQueenPlaced)
          {   delete newQueenPtr;
              removeQueen();
              queenPtr->nextRow();
          } // end if
       } // end if
    } // end while
    return isQueenPlaced;
} // end placeQueens