语言: Java
目标: 一般:解决数独游戏
具体:做一个递归方法solve():
问题: 循环尝试填充整数n,但总是先尝试最小的数字.如果我使用递归,整数将始终是相同的.
问题: 1.如何使代码填充1到9之间的数字.
如何使用递归来部分或完全擦除进度并尝试不同的数字.
(额外)我到目前为止构建的代码部分地解决了数独(直到空方块无法填充),但现在它甚至没有填充第一个方块,即使它之前做过.这不是我的主要问题,但如果有人注意到这个问题,我会非常感激,如果有人指出的话.
回顾: 我正在阅读关于递归的课程材料,但无法找到正确的信息.
免责声明: 方法printMatrix之外的所有println命令都用于测试
这是有问题的方法:
// prints all solutions that are extensions of current grid
// leaves grid in original state
void solve() {
//local variables
int[] currentSquare;
int currentRow;
int currentColumn;
boolean checkConflict;
currentSquare = new int[2];
//saftey limit for testing
int limit;
limit = 0;
while(findEmptySquare() != null){
currentSquare = findEmptySquare().clone();
currentRow = currentSquare[0];
currentColumn = currentSquare[1];
//System.out.println(" column c:"+currentColumn+" row r:"+currentRow); //column c5 r 3
if(currentSquare[0] != -1){
for(int n = 1; n <= ms; n++){
checkConflict = givesConflict(currentRow, currentColumn, n);
if(checkConflict == false){
grid[currentRow][currentColumn] = n;
}//end if
}//end for
}//end if
else{
System.out.println("solve: findEmptySquare was -1");
break;
}
//Safety limit
limit++;
if (limit > 20){
System.out.println("break");
break;
}//end if
}//end while
}
这是找到空方块的方法:
// finds the next empty square (in "reading order")
// returns array of first row then column coordinate
// if there is no empty square, returns .... (FILL IN!)
int[] findEmptySquare() {
int[] rowcol;
int[] noMoreCells;
rowcol = new int[2];
noMoreCells = new int[2];
noMoreCells[0] = -1;
noMoreCells[1] = -1;
for(int r = 0; r < ms; r++){
for(int c = 0; c < ms; c++){
if(grid[r][c] == 0){
if(r != rempty || c != cempty){ //check that the location of empty cell is not the same as last one
rempty = r;
cempty = c;
rowcol[0] = r; // 0 for row
rowcol[1] = c; // 1 for column
//System.out.println(" column c:"+rowcol[1]+" row r:"+rowcol[0]); //column c5 r 3
return rowcol;
}//end if
else{
System.out.println("findEmptySquare: found same empty square twice");
return noMoreCells;
}//end else
}//end if
}//end for
}//end for
System.out.println("findEmptySquare: no more empty cells");
return null; //no more empty cells
}
如果有必要,整个代码(缩进是杂乱的,因为我不得不在stackoverflow上手动添加空格):
// Alain Lifmann. Date: 26/9/2015
// Description of program: runs sudoku game
import java.util.*;
class Sudoku {
int ms = 9; //maze Size
int rempty; //keeping track of empty squares, row nr. (array)
int cempty; //keeping track of empty squares, column nr. (array)
int SIZE = 9; // size of the grid
int DMAX = 9; // maximal digit to be filled in
int BOXSIZE = 3; // size of the boxes
int[][] grid; // the puzzle grid; 0 represents empty
// a challenge-sudoku from the web
int[][] somesudoku = new int[][] {
{ 0, 6, 0, 0, 0, 1, 0, 9, 4 }, //original
// { 0, 0, 0, 0, 0, 1, 0, 9, 4 }, //to get more solutions
{ 3, 0, 0, 0, 0, 7, 1, 0, 0 },
{ 0, 0, 0, 0, 9, 0, 0, 0, 0 },
{ 7, 0, 6, 5, 0, 0, 2, 0, 9 },
{ 0, 3, 0, 0, 2, 0, 0, 6, 0 },
{ 9, 0, 2, 0, 0, 6, 3, 0, 1 },
{ 0, 0, 0, 0, 5, 0, 0, 0, 0 },
{ 0, 0, 7, 3, 0, 0, 0, 0, 2 },
{ 4, 1, 0, 7, 0, 0, 0, 8, 0 },
};
// a test-sudoku from oncourse
int[][] testsudoku = new int[][] {
{ 1, 2, 3, 4, 5, 6, 7, 8, 9 },
{ 4, 5, 6, 7, 8, 9, 1, 2, 3 },
{ 7, 8, 9, 1, 2, 3, 4, 5, 6 },
{ 2, 1, 4, 3, 6, 5, 8, 9, 7 },
{ 3, 6, 5, 8, 9, 7, 2, 1, 4 },
{ 8, 9, 7, 2, 1, 4, 3, 6, 5 },
{ 5, 3, 1, 6, 4, 2, 9, 7, 8 },
{ 6, 4, 2, 9, 7, 8, 5, 3, 1 },
{ 9, 7, 8, 5, 3, 1, 6, 4, 2 },
};
// a test-sudoku modified to be incomplete
int[][] testsudoku2 = new int[][] {
{ 0, 0, 3, 0, 5, 6, 7, 8, 0 },
{ 0, 5, 0, 7, 0, 0, 1, 0, 3 },
{ 7, 0, 0, 1, 0, 3, 4, 5, 6 },
{ 2, 1, 4, 3, 6, 5, 8, 0, 7 },
{ 3, 0, 5, 8, 0, 7, 0, 1, 0 },
{ 0, 9, 7, 0, 1, 4, 3, 0, 5 },
{ 0, 0, 0, 6, 4, 2, 9, 7, 8 },
{ 0, 4, 2, 9, 7, 8, 0, 0, 1 },
{ 0, 0, 0, 5, 3, 1, 0, 4, 0 },
};
int solutionnr = 0; //solution counter
// ----------------- conflict calculation --------------------
// is there a conflict when we fill in d at position r,c?
boolean givesConflict(int r, int c, int d) {
if(rowConflict(r, d) == true){
return true;
}//end if
if(colConflict(c, d) == true){
return true;
}//end if
if(boxConflict(r, c, d) == true){
return true;
}//end if
return false;
}//end givesConflict
boolean rowConflict(int r, int d) {
for(int i = 0; i < ms; i++){
if(d == grid[r][i]){
//System.out.println("rowconflict r:"+r+" d:"+d);
return true;
}//end if
}//end for
return false; //no conflict
}
boolean colConflict(int c, int d) {
for(int i = 0; i < ms; i++){
if(d == grid[i][c]){
//System.out.println("column conflict c:"+c+" d:"+d);
return true;
}//end if
}//end for
return false; //no conflict
}
boolean boxConflict(int rr, int cc, int d) { //test 5,3,1
int rs; // Box-row start point
int cs; // Box-column start point
rs = rr - rr%3;
cs = cc - cc%3;
//System.out.println("box start is row "+rs+" , column "+cs);
for(int r = rs; r < rs + 3; r++ ){
for(int c = cs; c < cs + 3; c++){
if(d == grid[r][c]){
//System.out.println("r:"+r+" c:"+c);
return true;
}//end if
}//end for
}//end for
return false; //no conflict
}
// --------- solving ----------
// finds the next empty square (in "reading order")
// returns array of first row then column coordinate
// if there is no empty square, returns .... (FILL IN!)
int[] findEmptySquare() {
int[] rowcol;
int[] noMoreCells;
rowcol = new int[2];
noMoreCells = new int[2];
noMoreCells[0] = -1;
noMoreCells[1] = -1;
for(int r = 0; r < ms; r++){
for(int c = 0; c < ms; c++){
if(grid[r][c] == 0){
if(r != rempty || c != cempty){ //check that the location of empty cell is not the same as last one
rempty = r;
cempty = c;
rowcol[0] = r; // 0 for row
rowcol[1] = c; // 1 for column
//System.out.println(" column c:"+rowcol[1]+" row r:"+rowcol[0]); //column c5 r 3
return rowcol;
}//end if
else{
System.out.println("findEmptySquare: found same empty square twice");
return noMoreCells;
}//end else
}//end if
}//end for
}//end for
System.out.println("findEmptySquare: no more empty cells");
return null; //no more empty cells
}
// prints all solutions that are extensions of current
// leaves grid in original state
void solve() {
//local variables
int[] currentSquare;
int currentRow;
int currentColumn;
boolean checkConflict;
currentSquare = new int[2];
//saftey limit for testing
int limit;
limit = 0;
while(findEmptySquare() != null){
currentSquare = findEmptySquare().clone();
currentRow = currentSquare[0];
currentColumn = currentSquare[1];
//System.out.println(" column c:"+currentColumn+" row r:"+currentRow); //column c5 r 3
if(currentSquare[0] != -1){
for(int n = 1; n <= ms; n++){
checkConflict = givesConflict(currentRow, currentColumn, n);
if(checkConflict == false){
grid[currentRow][currentColumn] = n;
}//end if
}//end for
}//end if
else{
System.out.println("solve: findEmptySquare was -1");
break;
}
//Safety limit
limit++;
if (limit > 20){
System.out.println("break");
break;
}//end if
}//end while
}
// ------------------------- misc -------------------------
// print the grid, 0s are printed as spaces
void printMatrix(){
int ms; //matrix Size
ms = 9;
//layer indication symbols
String end;
String mid;
String cut;
end = "+";
mid = "-";
cut = "";
for(int i = 0; i < 2*ms-1; i++){
cut = cut + mid;
}//end for
System.out.println(end+cut+end);
for(int i = 0; i < ms; i++){
if( i % 3 == 0 && i != 0){
System.out.println(mid+cut+mid);
}//end if
for(int j = 0; j < ms; j++){
if( j % 3 == 0){
System.out.print("|");
}//end if
else{
System.out.print(" ");
}//end else
if(grid[i][j] != 0){
System.out.print(grid[i][j]);
}//end if
else{
System.out.print(" ");
}//end else
}//end for j
System.out.print("|");
System.out.println();
}//end for i
System.out.println(end+cut+end);
}//end method
// reads the initial grid from stdin
void read() {
Scanner sc = new Scanner(System.in);
for (int r=0; r<SIZE; r++) {
if (r % BOXSIZE == 0) {
sc.nextLine(); // read away top border of box
}
for (int c=0; c < SIZE; c++) {
if (c % BOXSIZE == 0) {
sc.next(); // read away left border of box
}
String square = sc.next();
if (".".equals(square)) {
grid[r][c] = 0; // empty sqaure
} else {
grid[r][c] = Integer.parseInt(square);
}
//System.out.print(grid[r][c]);
}
sc.nextLine(); // read away right border
}
sc.nextLine(); // read away bottom border
}
// --------------- where it all starts --------------------
void solveIt() {
grid = somesudoku.clone(); // set used grid (before doing anything else)
printMatrix();
solve();
printMatrix();
/* test material
printMatrix();
//System.out.println(givesconflict(1,1,3));
System.out.println(rowConflict(0,1));
System.out.println(colConflict(0,1));
System.out.println(boxConflict(0,0,1));
findEmptySquare();
*/
}// end solveIt
public static void main(String[] args) {
new Sudoku().solveIt();
}
}
小智 0
这个问题可以通过回溯来解决。您必须递归遍历所有可能的选项，但当您遇到错误的问题时，请从该路径返回。您可以从此链接找到有关代码的帮助 http://learnfreecodes.blogspot.in/2015/11/sudoku-solver-using-backtracking-in-java.html