c - 将2D数组C代码转换为malloc

我制作了一个程序，将两个矩阵相加，并显示它们的和，最大维数为100。

/* This program asks the user for 2 matrices called A and B, as integers,
   and displays their sum, C. The max dimension of each matrix is 100. */

#include <stdio.h>

// Construct function
void construct()
{
   int m, n, i, j;      // Variables
   int first[100][100], second[100][100], sum[100][100]; // Matrices variables

   printf("Please enter the number of rows: ");
   scanf("%d", &m);
   printf("Please enter the number of columns: ");
   scanf("%d", &n);

   // User enters m x n amount whole numbers for the Matrix A
   printf("Enter Matrix A\n");
   for (i = 0; i < m; i++)
      for (j = 0; j < n; j++)
         scanf("%d", &first[i][j]);

   // User enters m x n amount whole numbers for the Matrix B
   printf("Enter Matrix B\n");
   for (i = 0; i < m; i++)
      for (j = 0; j < n; j++)
            scanf("%d", &second[i][j]);

   // Adds the sum of Matrix A and Matrix B
   for (i = 0; i < m; i++)
      for (j = 0; j < n; j++)
         sum[i][j] = first[i][j] + second[i][j];

   // Display the sum of Matrix A and Matrix B
   printf("A + B =\n");
   for (i = 0; i < m; i++)
   {
      for (j = 0; j < n; j++)
         printf("%d ", sum[i][j]);

      printf("\n"); // Prints new line
   }

   return ;
}

// Main Function
int main()
{
    construct(); // Calls construct function
    return 0;
}

现在，我需要更改它，以便每个矩阵都没有最大大小。
因此，我需要使用malloc创建我的数组。
所以我不能使用int A [rows] [cols]。
这就是我隐秘地将数组分配给malloc的方法。输入所有整数后，它可以编译但崩溃。需要帮忙。

/* This program asks the user for 2 matrices called A and B, as integers,
   and displays their sum, C. The max dimension of each matrix is 100. */

#include <stdio.h>
#include <stdlib.h>

// Construct function
void construct()
{
   int m, n, i, j;      // Variables
   int *first = NULL;
   int *second = NULL;
   int *sum = NULL;    // Matrices variables

   printf("Please enter the number of rows: ");
   scanf("%d", &m);
   printf("Please enter the number of columns: ");
   scanf("%d", &n);

   first = (int*)malloc(m * sizeof(int));
   second = (int*)malloc(n * sizeof(int));
   sum = (int*)malloc(m * n * sizeof(int));


   // User enters m x n amount whole numbers for the Matrix A
   printf("Enter Matrix A\n");
   for (i = 0; i < m; i++)
      for (j = 0; j < n; j++)
         scanf("%d", &first);

   // User enters m x n amount whole numbers for the Matrix B
   printf("Enter Matrix B\n");
   for (i = 0; i < m; i++)
      for (j = 0; j < n; j++)
            scanf("%d", &second);

   // Adds the sum of Matrix A and Matrix B
   for (i = 0; i < m; i++)
      for (j = 0; j < n; j++)
         sum = *first + *second;

   // Display the sum of Matrix A and Matrix B
   printf("A + B =\n");
   for (i = 0; i < m; i++)
   {
      for (j = 0; j < n; j++)
         printf("%d ", sum);

      printf("\n");
   }

   return ;
}

// Main Function
int main()
{
    construct(); // Calls construct function
    return 0;
}

最佳答案

首先，您不需要使用malloc。在输入m和n之后，只需将数组定义移动到：

int first[m][n];

printf("Enter Matrix A\n");
for (i = 0; i < m; i++)
    for (j = 0; j < n; j++)
        scanf("%d", &first[i][j]);

对于second和sum同样如此。

如果矩阵可能大于100x100，则最好使用malloc来避免堆栈溢出的风险。做到这一点的方法是：

int (*first)[n] = malloc(m * sizeof *first);

printf("Enter Matrix A\n");
// etc.

最后是free(first);。无需其他更改。



在尝试使用malloc时，您没有分配足够的空间，也没有scanf进入分配的空间（而是改写了指向已分配空间的指针）。

关于c - 将2D数组C代码转换为malloc，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/28788345/