c++ - Boyer Moore - 坏字符规则实现子串搜索

Question

我正在尝试使用 2D 数组从 boyer moore 实现错误字符规则以进行子字符串搜索，我遇到了我看到我的 arr[0][1] 与 arr[1][0] 重叠的情况这引起了问题。我试图遍历 VS 中的代码，如果我查看内存位置，它实际上会显示正确的值，但我不确定在打印重叠是如何发生的。有人可以帮助我了解我做错了什么吗？

错误输出j 的值为 --- 0

新条目是 --- f 102 13

while 循环内部 -- 102 13

while 循环内部 -- 13 -1 //13 的重叠发生 y ?

 # define ROWS 20
  # define COLUMNS 1

 int main(void)
    {
        string str = "firstcharacter";
        int strlength = str.length();
        int arr[ROWS][COLUMNS];
        memset(arr, -1, sizeof(arr[0][0]) * ROWS * COLUMNS);

        for (int i = 0; i < strlength; i++)
        {
            int j = 0;
            bool flag = false;
            // check till point previous character was inserted
            while (arr[j][1] != -1)
            {
                // if previous character is already present 
                // just update value dont insert character
                if (arr[j][0] == str[i])
                {
                    flag = true;
                    break;
                }
                j++;
            }

            if (flag == true)
            {
                int value = strlength - i - 1;
                arr[j][1] = value;
                cout << " Old entry is  --- " << str[i] << "  " << arr[j][0] << "     " << arr[j][1] << endl << endl;
            }
            else
            {
                int value = strlength - i - 1;
                arr[j][0] = str[i];
                arr[j][1] = value;
                cout << " New entry is  --- " << str[i] << "  "<< arr[j][0] << "     " << arr[j][1] << endl << endl;
            }   

            for (int x = 0; x < strlength; x++)
            {
                cout << " Inside while loop --  " << arr[x][0] << "     " << arr[x][1] << endl;      // --- error case after first iteration only I see value overlapping
            }
        }

        cout << endl << endl << endl << endl;

        for (int i = 0; i < strlength; i++)
        {
            cout << " final table is " << arr[i][0] << "     " << arr[i][1] << endl;
        }

        return 0;
    }

Answer 1

因为 COLUMNS 是 1。 ary[j][1] 和 ary[j+1][0] 将指向相同的内存地址，尽管第一个在技术上是未定义的行为，因为 [1] 下标超出范围，