c - 为什么在尝试将数组从标准输入复制到二维数组时出现段错误？

Question

这与 HackerRank Restaurant 问题有关，我已经用其他语言解决了这个问题，但现在正在尝试用 C 来解决。https://www.hackerrank.com/challenges/restaurant

我首先尝试存储结果 if read_slice_dimension()直接进入多维数组，但是因为我不能在不将数组设为静态的情况下将数组从函数传回，所以这是行不通的，因为每个嵌套数组都指向内存中相同的静态 2 整数数组，结果是每次都被覆盖read_slice_dimension()被称为，意味着我将有一个包含 num_slices 的数组指向从标准输入读入的最后一个数组的指针。

因此我决定尝试 memcpy , 这样我就可以从 read_slice_dimension() 复制 arry到一个新的内存块，以便它在我读取下一个切片时持续存在并且不会丢失。然而，似乎memcpy不是这样做的方法。什么是？

// Gets the number of slices for this test according to the first input value from stdin.
int read_num_slices() {
  int num_slices = 0;

  scanf("%i", &num_slices);

  if (num_slices == 0) {
    goto error;
  }

  return num_slices;

error:
  flag_error("ERROR: Could not parse the number of entries from first input line.");
}

// Gets a single line from stdin and attempts to parse it into a 2D int array representing the dimensions of a slice.
int* read_slice_dimension() {
  static int slice_dimension[2] = {0};

  scanf("%i %i", &slice_dimension[0], &slice_dimension[1]);

  if (slice_dimension[0] + slice_dimension[1] == 0) {
    goto error;
  }

  return slice_dimension;

error:
  flag_error("ERROR: Could not parse line entered into a 2 integer array representing the slice's dimensions.");
}

// Gets all of the bread slices to be processed.
//
// This function reads from stdin.  The first line should be a single integer that specifies the number of slices to be
// processed by this current test.  The subsequent lines should be two integers separated by a space which represent
// the 2D dimensions of each slice.
int** get_slices() {
  int num_slices = read_num_slices();
  static int** slices;
  slices = (int**)malloc(num_slices * sizeof(int*));

  int i = 0;
  for (i; i < num_slices; i++) {
    int* slice = slices[i];
    slice = (int*)malloc(2 * sizeof(int));
    memcpy(slice, read_slice_dimension(), 2 * sizeof(int));
    printf("%i %i\n", slices[i][0], slices[i][1]); // CAUSES SEGMENTATION FAULT
  }

  return slices;
}

Answer 1

您正在设置 slice = slices[i]，然后调用 malloc。那是倒退。调用malloc，然后设置slices[i]。 – 用户 3386109