數獨C遞歸函數無法正常工作

Question

我在c中製作了一個數獨求解器，而遞歸函數只對第一行起作用，而不是停止。它尋找值爲零的第一個元素並填充它，然後查找下一個值，並用另一個解決方案填充它。在它解決了第一行之後，我將如何啓用canSolve，遞歸功能貫穿整個董事會...... sudokuGrid也是全球性的。

//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

將遞歸與全局變量結合使用通常不是一個好主意。如果你的求解器做出錯誤的選擇並需要回溯，它還需要將板恢復到它做出該選擇時的狀態。

那麼你需要做什麼？

我猜你需要嘗試下一個候選之前擦拭董事會其他成員：

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