我正在尝试使用回溯跟踪广告递归写一个数独求解器，当我完成所有事情时，我的输出只是“[]”，括号中没有任何内容。 我的预期输出应该是我测试仪中的3解决方案。
package sudoku;
import java.util.*;
public class Grid
{
private int[][] values;
// Dots in input strings become 0s in values[][].
//
public Grid(String []rows )
{
values = new int[9][9];
for (int j=0; j<9; j++)
{
String row = rows[j];
char[] charray = row.toCharArray();
for (int i=0; i<9; i++)
{
char ch = charray[i];
if (ch != '.')
values[j][i] = ch - '0';
}
}
}
public Grid(Grid grid) {
this.grid = grid;
}
public String toString()
{
String s = "";
for (int j=0; j<9; j++)
{
for (int i=0; i<9; i++)
{
int n = values[j][i];
if (n == 0)
s += '.';
else
s += (char)('0' + n);
}
s += "\n";
}
return s;
}
//
// Finds an empty member of values[][]. Returns an array list of 9 grids that look like the current grid,
// except the empty member contains 1, 2, 3 .... 9. Returns null if the current grid is full.
//
public ArrayList<Grid> next9Grids(){
if(this.isFull())
{
return null;
}
else
{
ArrayList<Grid> grids = new ArrayList<>();
for(int i = 0; i < 9;i++)
{
for(int j = 0; j< 9 ;j++)
{
if(values[i][j] == 0)
{
for(int k = 1; k<=9;k++)
{
Grid theGrid = new Grid(this);
theGrid.values[i][j] = k;
grids.add(theGrid);
}
}
}
}
return grids;
}
}
// Returns true if this grid is legal. A grid is legal if no row, column, or zone contains
// a repeated 1, 2, 3, 4, 5, 6, 7, 8, or 9.
//
public boolean isLegal()
{
int row = 0;
int col = 0;
int num =0;
for( col = 0; col < 9; col++ )
if( values[row][col] == num )
return false ;
for( row = 0; row < 9; row++ )
if( values[row][col] == num )
return false ;
row = (row / 3) * 3 ;
col = (col / 3) * 3 ;
for( int r = 0; r < 3; r++ )
for( int c = 0; c < 3; c++ )
if( values[row+r][col+c] == num )
return false ;
return true;
}
// Returns true if every cell member of values[][] is a digit from 1-9.
//
public boolean isFull()
{
int min = 1;
int max = 9;
for (int i = 0; i < values.length; i++)
{
for (int j = 0; j < values[0].length; j++)
{
if (values[i][j] < min || values[i][j] > max)
{
return false;
}
}
}
return true;
}
// Returns true if x is a Grid and, for every (i,j),
// x.values[i][j] == this.values[i][j].
//
public boolean equals(Grid that)
{
Grid x = (Grid)that;
if (x.equals(this))
{
for (int i = 0; i < 9; i++)
{
for (int j = 0; j < 9; j++)
{
if (that.values[i][j] == this.values[i][j])
{
return true;
}
}
}
}
return false;
}
}
package sudoku;
import java.util.*;
public class Solver
{
private Grid problem;
private ArrayList<Grid> solutions;
public Solver(Grid problem)
{
this.problem = problem;
solutions = new ArrayList<Grid>();
}
public ArrayList<Grid> solve()
{
solutions = new ArrayList<>();
solveRecurse(problem);
return solutions;
}
// Standard backtracking recursive solver.
//
private void solveRecurse(Grid grid)
{
Evaluation eval = evaluate(grid);
if (eval == Evaluation.ABANDON)
{
return;
}
else if (eval == Evaluation.ACCEPT)
{
solutions.add(grid);
}
else
{
ArrayList<Grid> array = grid.next9Grids();
for (Grid i: array)
{
solveRecurse(i);
// Here if eval == Evaluation.CONTINUE.
}
}
}
// Returns Evaluation.ABANDON if the grid is illegal.
// Returns ACCEPT if the grid is legal and complete.
// Returns CONTINUE if the grid is legal and incomplete.
//
public Evaluation evaluate(Grid grid)
{
if(!grid.isLegal())
{
return Evaluation.ABANDON;
}
else if(grid.isLegal() && grid.isFull())
{
return Evaluation.ACCEPT;
}
else
return Evaluation.CONTINUE;
}
public ArrayList<Grid> getSolutions()
{
return solutions;
}
public static void main(String[] args)
{
Grid g = TestGridSupplier.getPuzzle1(); // or any other puzzle
Solver solver = new Solver(g);
solver.solve();
System.out.println(solver.getSolutions());
// Print out the solution
}
以下是我的测试人员
package sudoku;
public class TestGridSupplier
{
private final static String[] PUZZLE_1 =
{
"..3.1.5..",
"8..395..1",
"15.....27",
".8..7..5.",
"62.9.4.13",
".9..2..7.",
"91.....34",
"2..748..9",
"..6.3.2.."
};
private final static String[] SOLUTION_1 =
{
"463217598",
"872395641",
"159486327",
"384671952",
"627954813",
"591823476",
"918562734",
"235748169",
"746139285"
};
static Grid getPuzzle1() { return new Grid(PUZZLE_1); }
static Grid getSolution1() { return new Grid(SOLUTION_1); }
private final static String[] PUZZLE_2 =
{
".........",
"8.1...9.7",
"..75493..",
"7..9.2..8",
"....1....",
"1..3.8..5",
"..84312..",
"2.5...1.9",
"........."
};
private final static String[] SOLUTION_2 =
{
"439187562",
"851623947",
"627549381",
"763952418",
"582714693",
"194368725",
"978431256",
"245876139",
"316295874"
};
static Grid getPuzzle2() { return new Grid(PUZZLE_2); }
static Grid getSolution2() { return new Grid(SOLUTION_2); }
private final static String[] PUZZLE_3 =
{
".97..1.6.",
"2....7..5",
"....9...3",
"85.......",
"..9...5..",
".......32",
"3...7....",
"5..6....1",
".4.1..37."
};
private final static String[] SOLUTION_3 =
{
"497351268",
"236847195",
"185296743",
"853924617",
"629713584",
"714568932",
"361472859",
"578639421",
"942185376"
};
static Grid getPuzzle3() { return new Grid(PUZZLE_3); }
static Grid getSolution3() { return new Grid(SOLUTION_3); }
//
// You can use these to test your Grid's evaluate() method.
//
private final static String[] REJECT_1 =
{
"11.......",
".........",
".........",
".........",
".........",
".........",
".........",
".........",
"........."
};
private final static String[] REJECT_2 =
{
"2........",
"2........",
".........",
".........",
".........",
".........",
".........",
".........",
"........."
};
private final static String[] REJECT_3 =
{
"3........",
"..3......",
".........",
".........",
".........",
".........",
".........",
".........",
"........."
};
private final static String[] REJECT_4 =
{
".........",
".........",
".........",
"....4....",
".....4...",
".........",
".........",
".........",
"........."
};
private final static String[] CONTINUE =
{
"123456789",
".........",
".........",
".........",
".........",
".........",
".........",
".........",
"........."
};
static Grid getReject1() { return new Grid(REJECT_1); }
static Grid getReject2() { return new Grid(REJECT_2); }
static Grid getReject3() { return new Grid(REJECT_3); }
static Grid getReject4() { return new Grid(REJECT_4); }
static Grid getContinue() { return new Grid(CONTINUE); }
static Grid getAccept() { return getSolution1(); }
}