Question

我在c中做了一个数独求解器，我的递归函数只适用于第一行而不是停止。它查找值为零的第一个元素并填充它然后查找下一个值，并用另一个解决方案填充它。解决了它停止的第一行后，如何启用canSolve，递归函数遍历整个板... sudokuGrid也是全局的。

//this function makes a list of possible values for an empty cell, candidateList.
//candidateList is global so it  the list can be accesed by the recursive solver function:
//canSolve();
void verifyCell(int x, int y){
    int i;
    int j;

    for (i=0; i<9; i++){
        candidateList[i] = 0;
    }
    //Rows
    for (j=0; j<cols; j++){
        if(sudokuGrid[x][j] != 0){
           candidateList[sudokuGrid[x][j] - 1] = 1;
        }
    }
    //Columns
   for (i=0; i<rows; i++){
        if(sudokuGrid[i][y] != 0){
           candidateList[sudokuGrid[i][y] - 1] = 1;
        }
    }
    //blocks
    int startRow = ((x/3)*3);
    int startCol = ((x/3)*3);
    for (i = startRow; i<startRow+3; i++){
        for(j=startCol;j<startCol+3;j++){
            if(sudokuGrid[i][j] != 0){
               candidateList[sudokuGrid[i][j] - 1] = 1;
            }
       }
    }
    for(i = 0; i<9;i++){
        if (candidateList[i]==0){
            candidateList[i] = i+1;
        }else{
            candidateList[i] = 0;
        }
    }
    return;
}

 canSolve(){
    int i;
    int j;
    int x;
    int y;
    x= 0;
    y = 0;
    //gridToString();
    if (isSolved()==1){
        printf("Great this grid is Solved!\n");
        gridToString();
        return;
    }
    for(i=0;i<rows;i++){
        for(j=0;j<cols;j++){
            if(sudokuGrid[i][j]==0){
                x=i;
                y=j;
            }
        }
        goto rest;
    }
    printf("(%d, %d)", x, y);
    rest:;
    verifyCell(x,y);

    for(i = 0; i<rows; i++){
        printf("%d", candidateList[i]);
        if (candidateList[i] != 0){
            sudokuGrid[x][y]=candidateList[i];
            gridToString();
            canSolve();//By the end of solving the first row it stops
        }else{
            sudokuGrid[x][y]=sudokuGrid[x][y];
        }
    }
}

Answer 1

将递归与全局变量结合使用通常不是一个好主意。如果你的求解器做出了错误的选择并且需要回溯它，那么还需要将板恢复到它做出选择时的状态。

那你需要做什么？

我想你需要在尝试下一个候选人之前擦掉剩余的棋盘：

        canSolve();//By the end of solving the first row it stops
        wipeRestOfBoard(x,y);  // Put 0 in sudokuGrid[x,y] and subsequent positions
    }else{

Sudoku C递归函数无法正常工作

1 个答案: