Пример #1
0
T MaxLoading(T w[], T c, int n)
{// Return value of best loading.
 // Use FIFO branch and bound.
   // initialize for level 1 start
   LinkedQueue<T> Q;  // live-node queue
   Q.Add(-1);         // end-of-level marker
   int i = 1;         // level of E-node
   T Ew = 0,          // weight of E-node
     bestw = 0;       // best weight so far

   // search subset space tree
   while (true) {
      // check left child of E-node
      if (Ew + w[i] <= c) // x[i] = 1
         AddLiveNode(Q, Ew + w[i], bestw, i, n);

      // right child is always feasible
      AddLiveNode(Q, Ew, bestw, i, n); // x[i] = 0

      Q.Delete(Ew);     // get next E-node
      if (Ew == -1) {   // end of level
         if (Q.IsEmpty()) return bestw;
         Q.Add(-1);     // end-of-level marker
         Q.Delete(Ew);  // get next E-node
         i++;}          // level number of Ew
      }
}
Пример #2
0
bool FindPath(Position start, Position finish,
             int& PathLen, Position * &path)
{// Find a path from start to finish.
 // Return true if successful, false if impossible.
 // Throw NoMem exception if inadequate space.

   if ((start.row == finish.row) &&
      (start.col == finish.col))
         {PathLen = 0; return true;} // start = finish

   // initialize wall of blocks around grid
   for (int i = 0; i <= m+1; i++) {
      grid[0][i] = grid[m+1][i] = 1; // bottom & top
      grid[i][0] = grid[i][m+1] = 1; // left & right
      }

   // initialize offsets
   Position offset[4];
   offset[0].row = 0; offset[0].col = 1; // right
   offset[1].row = 1; offset[1].col = 0; // down
   offset[2].row = 0; offset[2].col = -1; // left
   offset[3].row = -1; offset[3].col = 0; // up

   int NumOfNbrs = 4; // neighbors of a grid position
   Position here, nbr;
   here.row = start.row;
   here.col = start.col;
   grid[start.row][start.col] = 2; // block
   
   // label reachable grid positions
   LinkedQueue<Position> Q;
   do {// label neighbors of here
      for (int i = 0; i < NumOfNbrs; i++) {
         nbr.row = here.row + offset[i].row;
         nbr.col = here.col + offset[i].col;
         if (grid[nbr.row][nbr.col] == 0) {
             // unlabeled nbr, label it
             grid[nbr.row][nbr.col]
                = grid[here.row][here.col] + 1;
             if ((nbr.row == finish.row) &&
                (nbr.col == finish.col)) break; // done
   	     Q.Add(nbr);} // end of if
         } // end of for
      
      // have we reached finish?
      if ((nbr.row == finish.row) &&
          (nbr.col == finish.col)) break; // done

      // finish not reached, can we move to a nbr?
      if (Q.IsEmpty()) return false; // no path
      Q.Delete(here); // get next position
   } while(true);
            
   // construct path
   PathLen = grid[finish.row][finish.col] - 2;
   path = new Position [PathLen];

   // trace backwards from finish
   here = finish;
   for (int j = PathLen-1; j >= 0; j--) {
      path[j] = here;
      // find predecessor position
      for (int i = 0; i < NumOfNbrs; i++) {
         nbr.row = here.row + offset[i].row;
         nbr.col = here.col + offset[i].col;
         if (grid[nbr.row][nbr.col] == j+2) break;
         }
      here = nbr;  // move to predecessor
      }

   return true;
}