数独回溯无效的数独

数独回溯无效的数独

当然，当您触及

sudo[row][col] = 0;

代码时，您刚刚尝试了平方中的每个值，但找不到任何解决方案。当然，这是您决定放弃无解决方案状态的关键所在。

进一步考虑-我怀疑我几乎是正确的。如果您遇到此代码， 并且 这是您尝试的 第一个 单元（即找到的第一个空单元），那么这就是您的失败时刻。

顺便说一句-我不确定使用Exception来指示您在注释中建议的解决方案是一个好主意。

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现在，这可以正确地拒绝您发布的木板-请注意，第一行不仅有两个“ 3”，而且在第一列中也有两个“
5”。该代码现在似乎对我有用。也许您可以在一个无法解决的问题上尝试一下。

public class Test {    static final int S = 9;    int[][] sudo;    public Test() {        // Just leave it empty.        sudo = new int[S][S];    }    public Test(int[][] sudo) {        this.sudo = sudo;    }    // This number should not appear anywhere in the row.    public boolean checkHorizontal(int row, int num) {        for (int i = 0; i < S; i++) { if (sudo[row][i] == num) {     return false; }        }        return true;    }    // This number should not appear anywhere in the col.    public boolean checkVertical(int col, int num) {        for (int i = 0; i < S; i++) { if (sudo[i][col] == num) {     return false; }        }        return true;    }    // This number should not appear anywhere in the box.    private boolean checkBox(int row, int col, int num) {        // Round down to nearest 3.        int r = (row / 3) * 3;        int c = (col / 3) * 3;        for (int i = r; i < r + 3; i++) { for (int j = c; j < c + 3; j++) {     if (sudo[i][j] == num) {         return false;     } }        }        return true;    }    boolean check(int row, int col, int num) {        // All checks must pass.        return checkHorizontal(row, num)     && checkVertical(col, num)     && checkBox(row, col, num);    }    public boolean solve(int row, int col) {        // Got to the end?        if (row >= S) { //Gelöst return true;        }        // If the cell is empty        if (sudo[row][col] == 0) { // Find a valid number for the empty cell for (int num = 1; num < 10; num++) {     // Can this number be put there?     if (check(row, col, num)) {         // Yes!         sudo[row][col] = num;         // Try that.         if (next(row, col)) {  return true;         }     } } // Clean up. sudo[row][col] = 0;        } else { // Move on. if (next(row, col)) {     return true; }        }        // Failed to find a solution.        return false;    }    //Ruft solve für das nächste Feld auf    public boolean next(int row, int col) {        if (col < S - 1) { // Step right. return solve(row, col + 1);        } else { // Step down. return solve(row + 1, 0);        }    }    public boolean boardOk() {        // Initial test to ensure it is a valid array.        // Must have that many rows.        boolean ok = sudo.length == S;        for (int row = 0; ok && row < S; row++) { // Each row must be that long. ok &= sudo[row].length == S; for (int col = 0; ok && col < S; col++) {     // Each filled square must be valid.     if (sudo[row][col] != 0) {         int num = sudo[row][col];         // Remove it.         sudo[row][col] = 0;         // Check it can be added.         ok &= check(row, col, num);         // Put it back.         sudo[row][col] = num;     } }        }        return ok;    }    void solve() {        if (boardOk()) { boolean solved = solve(0, 0); if (solved) {     System.out.println("Solved!");     print(); }        } else { System.out.println("Insoluble!"); print();        }    }    public void print() {        for (int i = 0; i < sudo.length; i++) { System.out.println(Arrays.toString(sudo[i]));        }    }        public static void main(String[] args) {        new Test().solve();        int[][] test = { {0, 0, 6, 5, 8, 3, 3, 2, 7}, {0, 0, 0, 0, 9, 0, 0, 5, 0}, {5, 8, 0, 0, 0, 0, 0, 0, 3}, {0, 3, 1, 0, 4, 0, 5, 0, 0}, {0, 0, 0, 9, 2, 0, 3, 0, 6}, {0, 0, 0, 0, 0, 0, 0, 0, 1}, {3, 4, 2, 0, 0, 6, 9, 1, 5}, {5, 0, 5, 4, 0, 9, 0, 3, 2}, {0, 1, 0, 0, 0, 0, 0, 0, 4},};        new Test(test).solve();    }}