在c中打印二维数组

I am trying to define a two dimensional array by initially defining elements for 5 x 2 matrix and then I am defining again the elements for 6th row. But when I try to print the elements of this matrix I am getting 0 and 5 for the last value. Tried same by defining elements again for 4th or 6th row but then it is working fine.

我试图通过最初定义5 x 2矩阵的元素来定义二维数组,然后我再次定义第6行的元素。但是当我尝试打印这个矩阵的元素时,我得到0和5代表最后一个值。通过为第4行或第6行再次定义元素来尝试相同但是它工作正常。

#include<math.h>
#include<stdio.h>
main()
{
  int arr[ ][2]={{11,12},{21,22},{31,32},{41,42},{51,52}};
  int i, j;
  arr[5][0]=61; arr[5][1]=62;
  for (i=0;i<=5;i++)
  {
    for (j=0;j<=1;j++)
    {
      printf ("%d \n", arr[i][j]);
    }
  }
}

1 个解决方案

#1

Your initialised array is given exactly enough memory to hold the specified data values. So

初始化的数组具有足够的内存来保存指定的数据值。所以

int arr[ ][2]={{11,12},{21,22},{31,32},{41,42},{51,52}};

creates the array as int arr[5][2] and then the line

创建数组为int arr [5] [2]然后是行

arr[5][0]=61; arr[5][1]=62;

exceeds the array bounds. The maximum index is [4][1] because array indexing is 0 based. If you want to add another element you should specify

超出数组范围。最大索引是[4] [1],因为数组索引是基于0的。如果要添加另一个元素,则应指定

int arr[6][2]={{11,12},{21,22},{31,32},{41,42},{51,52}};

and then this line will work.

然后这一行将起作用。

arr[5][0]=61; arr[5][1]=62;

An alternative would be to use malloc() to allocate memory for the array, and then if you want to add another row you can use realloc(), and this shows how to make a flexible array.

另一种方法是使用malloc()为数组分配内存,然后如果要添加另一行,可以使用realloc(),这将显示如何创建一个灵活的数组。

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

#define COLUMNS 2
#define ROWS 5

typedef int rowtype[COLUMNS];

int main() {
    int i, j;
    rowtype *array = malloc(ROWS * sizeof(rowtype));
    if (array == NULL)
        return -1;

    for (j=0; j<ROWS; j++)
        for (i=0; i<COLUMNS; i++)
            array[j][i] = (j+1)*10 + (i+1);

    for (j=0; j<ROWS; j++) {
        for (i=0; i<COLUMNS; i++)
            printf ("%-4d", array[j][i]);
        printf ("\n");
    }

    printf("Add another row\n");
    array = realloc(array, (ROWS+1) * sizeof(rowtype));
    if (array == NULL)
        return -1;
    array[ROWS][0] = 61;
    array[ROWS][1] = 62;

    for (j=0; j<ROWS+1; j++) {
        for (i=0; i<COLUMNS; i++)
            printf ("%-4d", array[j][i]);
        printf ("\n");
    }

    free(array);
    return 0;
}

Program output:

11  12
21  22
31  32
41  42
51  52
Add another row
11  12
21  22
31  32
41  42
51  52
61  62

#1