掃雷程序C ++的分段錯誤

Question

我認為問題出在我的構造函數中。 它開始運行並將炸彈“放入”二維數組（網格），但在中間停止。 （有時它會貫穿整個過程...

SweeperGrid::SweeperGrid(const int initialRows, const int initialCols, const int density){
if ((initialRows<5 || initialCols<5) || (density<25 || density>75)) {
    throw out_of_range("Grid not large enough (number of rows or columns cannot be fewer than 5) or density is too low or high (must be between 25% and 75%)");
}

numRows = initialRows;
numColumns = initialCols;
numBombs = 0;

grid = new SweeperCell*[numRows];
for(int i=0; i <numRows; i++){
    grid[i] = new SweeperCell[numColumns];
}

srand(time(0));
for(int i=0; i<numRows; i++){
    for (int j=0; j<numColumns; j++){
        if(rand()%100+1<=density){
            PlaceBomb(i, j);
        }
    }
}
}

這是PlaceBomb函數：

void SweeperGrid::PlaceBomb(int row, int col){
cout<<row<<", "<<col<<endl;

if ((row<0||row>=numRows)||(col<0||col>=numColumns)){
    throw out_of_range("Out of bounds (PlaceBomb)");
}

At(row, col).PlaceBomb();
numBombs++;

//add if statements so it doesn't go out of bounds
if (row==0) {
    At(row+1, col).IncrementNumAdjacent();
    At(row, col-1).IncrementNumAdjacent();
    At(row, col+1).IncrementNumAdjacent();
    At(row+1, col+1).IncrementNumAdjacent();
    At(row+1, col-1).IncrementNumAdjacent();
}

if (row==0&&col==0) {
    At(row+1, col).IncrementNumAdjacent();
    At(row, col+1).IncrementNumAdjacent();
    At(row+1, col+1).IncrementNumAdjacent();
}

if (col==0) {
    At(row-1, col).IncrementNumAdjacent();
    At(row+1, col).IncrementNumAdjacent();
    At(row, col+1).IncrementNumAdjacent();
    At(row+1, col+1).IncrementNumAdjacent();
    At(row-1, col+1).IncrementNumAdjacent();
}

if (row==numRows-1) {
    At(row-1, col).IncrementNumAdjacent();
    At(row, col-1).IncrementNumAdjacent();
    At(row, col+1).IncrementNumAdjacent();
    At(row-1, col-1).IncrementNumAdjacent();
    At(row-1, col+1).IncrementNumAdjacent();
}

if (row==numRows-1&&col==numColumns-1) {
    At(row-1, col).IncrementNumAdjacent();
    At(row, col-1).IncrementNumAdjacent();
    At(row-1, col-1).IncrementNumAdjacent();
}

if (col==numColumns-1) {
    At(row-1, col).IncrementNumAdjacent();
    At(row+1, col).IncrementNumAdjacent();
    At(row, col-1).IncrementNumAdjacent();
    At(row-1, col-1).IncrementNumAdjacent();
    At(row+1, col-1).IncrementNumAdjacent();
}

if (row==0&&col==numColumns-1) {
    At(row+1, col).IncrementNumAdjacent();
    At(row, col-1).IncrementNumAdjacent();
    At(row+1, col-1).IncrementNumAdjacent();
}

if (row==numRows-1&&col==0) {
    At(row-1, col).IncrementNumAdjacent();
    At(row, col+1).IncrementNumAdjacent();
    At(row-1, col+1).IncrementNumAdjacent();
}

** IncrementNumAdjacent在另一個文件中，我確定它可以工作。

Answer 1

您的IncrementNumAdjacent調用過多，其中一些可能超出范圍。

例如：

if (row==0) {
    At(row+1, col).IncrementNumAdjacent();
    At(row, col-1).IncrementNumAdjacent();

如果此時col為0會怎樣？

在您的SweeperGrid類中擁有一個safeIncrementNumAdjacent(int row, int col)方法可能會更容易，而該方法只是忽略了超出范圍的項目。 就像是：

void SweeperGrid::safeIncrementNumAdjacent(int row, int col) {
   if (row >= 0 && row < numRows && col >= 0 & col < numCols)
      At(row, col).IncrementNumAdjacent();
}

然后只需調用當前點周圍的8個位置即可。