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C：2次元配列のサイズ

2次元配列の行と列を数える助けが必要です。列を数えられないようです？

#include <stdio.h>

int main() {

char result[10][7] = {

    {'1','X','2','X','2','1','1'},
    {'X','1','1','2','2','1','1'},
    {'X','1','1','2','2','1','1'},
    {'1','X','2','X','2','2','2'},
    {'1','X','1','X','1','X','2'},
    {'1','X','2','X','2','1','1'},
    {'1','X','2','2','1','X','1'},
    {'1','X','2','X','2','1','X'},
    {'1','1','1','X','2','2','1'},
    {'1','X','2','X','2','1','1'}

};

int row = sizeof(result) / sizeof(result[0]);
int column = sizeof(result[0])/row;

printf("Number of rows: %d\n", row);
printf("Number of columns: %d\n", column);

}

出力：
行数：10
列数：0

carraysdimensional
14
Wickerman

それは整数除算の問題です！

_int column = sizeof(result[0])/row;
_

あるべき

_int column = 7 / 10;
_

整数除算では、_7/10==0_。

あなたがしたいことは、1行の長さを分割することです。 sizeof(result[0])は、その行の1つの要素のサイズで、たとえばsizeof(result[0][0])：

_int column = sizeof(result[0])/sizeof(result[0][0]);
_
8
Marcus Müller

配列長マクロを使用する方がはるかに便利です（エラーが発生しにくくなります）。

#include <stdio.h>

#define LEN(arr) ((int) (sizeof (arr) / sizeof (arr)[0]))

int main(void)
{
    char result[10][7];

    printf("Number of rows: %d\n", LEN(result));
    printf("Number of columns: %d\n", LEN(result[0]));
    return 0;
}
10
August Karlstrom

これは私のために機能します（コメントはwhyを説明します）：

#include <stdio.h>

int main() {

   char result[10][7] = {

       {'1','X','2','X','2','1','1'},
       {'X','1','1','2','2','1','1'},
       {'X','1','1','2','2','1','1'},
       {'1','X','2','X','2','2','2'},
       {'1','X','1','X','1','X','2'},
       {'1','X','2','X','2','1','1'},
       {'1','X','2','2','1','X','1'},
       {'1','X','2','X','2','1','X'},
       {'1','1','1','X','2','2','1'},
       {'1','X','2','X','2','1','1'}

   }; 

   // 'total' will be 70 = 10 * 7
   int total = sizeof(result);

   // 'column' will be 7 = size of first row
   int column = sizeof(result[0]);

   // 'row' will be 10 = 70 / 7
   int row = total / column;

   printf("Total fields: %d\n", total);
   printf("Number of rows: %d\n", row);
   printf("Number of columns: %d\n", column);

}

そして、これの出力は次のとおりです。

Total of fields: 70
Number of rows: 10
Number of columns: 7

編集：

@AnorZakenが指すように、配列をパラメーターとして関数に渡し、sizeofの結果を出力すると、別のtotalが出力されます。これは、配列へのポインタではなく引数として配列を渡すと、Cはそれをコピーとして渡し、間にCマジックを適用するため、あなたが思っているとおりに正確に渡さないからです。何をしているのかを確認し、余分なCPU作業とメモリ消費を避けるために、配列とオブジェクトを参照によって（ポインタを使用して）渡すことをお勧めします。したがって、次のようなものを使用して、元の結果と同じ結果を得ることができます。

#include <stdio.h>

void foo(char (*result)[10][7])
{
   // 'total' will be 70 = 10 * 7
   int total = sizeof(*result);

   // 'column' will be 7 = size of first row
   int column = sizeof((*result)[0]);

   // 'row' will be 10 = 70 / 7
   int row = total / column;

   printf("Total fields: %d\n", total);
   printf("Number of rows: %d\n", row);
   printf("Number of columns: %d\n", column);

}

int main(void) {

   char result[10][7] = {

       {'1','X','2','X','2','1','1'},
       {'X','1','1','2','2','1','1'},
       {'X','1','1','2','2','1','1'},
       {'1','X','2','X','2','2','2'},
       {'1','X','1','X','1','X','2'},
       {'1','X','2','X','2','1','1'},
       {'1','X','2','2','1','X','1'},
       {'1','X','2','X','2','1','X'},
       {'1','1','1','X','2','2','1'},
       {'1','X','2','X','2','1','1'}

   };

   foo(&result);

   return 0;
}
8
emi

以下のコードに示すマクロを使用して、1D、2D、または3D配列の任意の次元サイズを取得します。同様に、4D配列以上の寸法を取得するために、より多くのマクロを作成できます。 （私はウィッカーマンが見るには遅すぎることを知っていますが、これらはこのページにアクセスする他の人のためのものです）

// Output of the following program
// [
/*

Demo of the advertised macros :
----------------------------------------------
sizeof(int) = 4
sizeof(Array_1D) = 12
ELEMENTS_IN_1D_ARRAY(Array_1D) = 3
sizeof(Array_2D) = 24
ELEMENTS_IN_2D_ARRAY(Array_2D) = 6
ROWS_IN_2D_ARRAY(Array_2D) = 2
COLUMNS_IN_2D_ARRAY(Array_2D) = 3
sizeof(Array_3D) = 96
ELEMENTS_IN_3D_ARRAY(Array_3D) = 24
MATRICES_IN_3D_ARRAY(Array_3D) = 4
ROWS_IN_3D_ARRAY(Array_3D) = 2
COLUMNS_IN_3D_ARRAY(Array_3D) = 3

Array_3D[][][] Printed :
----------------------------------------------
 001 002 003
 011 012 013
---------------
 101 102 103
 111 112 113
---------------
 201 202 203
 211 212 213
---------------
 301 302 303
 311 312 313
---------------

Wickerman's problem solved :
----------------------------------------------
sizeof(result) = 70
ELEMENTS_IN_2D_ARRAY(result) = 70
ROWS_IN_2D_ARRAY(result) = 10
COLUMNS_IN_2D_ARRAY(result) = 7

*/
// ]

// ====================================================================================================
// Program follows
// ====================================================================================================

// Array Size Macros
// [
#define ELEMENTS_IN_1D_ARRAY(a1D)   ( sizeof( a1D       ) / sizeof( a1D[0]          )) // Total no. of elements in 1D array
#define ELEMENTS_IN_2D_ARRAY(a2D)   ( sizeof( a2D       ) / sizeof( a2D[0][0]       )) // Total no. of elements in 2D array
#define ROWS_IN_2D_ARRAY(a2D)       ( sizeof( a2D       ) / sizeof( a2D[0]          )) // No. of Rows in a 2D array
#define COLUMNS_IN_2D_ARRAY(a2D)    ( sizeof( a2D[0]    ) / sizeof( a2D[0][0]       )) // No. of Columns in a 2D array
#define ELEMENTS_IN_3D_ARRAY(a3D)   ( sizeof( a3D       ) / sizeof( a3D[0][0][0]    )) // Total no. of elements in 3D array
#define MATRICES_IN_3D_ARRAY(a3D)   ( sizeof( a3D       ) / sizeof( a3D[0]          )) // No. of "Matrices" (aka "Slices"/"Pages") in a 3D array
#define ROWS_IN_3D_ARRAY(a3D)       ( sizeof( a3D[0]    ) / sizeof( a3D[0][0]       )) // No. of Rows in each "Matrix" of a 3D array
#define COLUMNS_IN_3D_ARRAY(a3D)    ( sizeof( a3D[0][0] ) / sizeof( a3D[0][0][0]    )) // No. of Columns in each "Matrix" of a 3D array
// ]

#define PRINTF_d(s) (printf(#s " = %d\n", (int)(s)))    // Macro to print a decimal no. along with its corresponding decimal expression string,
                                                        // while avoiding to write the decimal expression twice.

// Demo of the Array Size Macros defined above
// [
main()
{
    // Sample array definitions
    // [
    int Array_1D[3] = {1, 2, 3};    // 1D array

    int Array_2D[2][3] =            // 2D array
    {
        {1,  2,  3},
        {11, 12, 13}
    };

    int Array_3D[4][2][3] =         // 3D Array
    {
        {
            {1,   2,   3},
            {11,  12,  13}
        },
        {
            {101, 102, 103},
            {111, 112, 113}
        },
        {
            {201, 202, 203},
            {211, 212, 213}
        },
        {
            {301, 302, 303},
            {311, 312, 313}
        }
    };
    // ]

    // Printing sizes and dimensions of arrays with the advertised Array Size Macros
    printf(
    "Demo of the advertised macros :\n"
    "----------------------------------------------\n");
    PRINTF_d(sizeof(int));
    PRINTF_d(sizeof(Array_1D));
    PRINTF_d(ELEMENTS_IN_1D_ARRAY(Array_1D));
    PRINTF_d(sizeof(Array_2D));
    PRINTF_d(ELEMENTS_IN_2D_ARRAY(Array_2D));
    PRINTF_d(ROWS_IN_2D_ARRAY(Array_2D));
    PRINTF_d(COLUMNS_IN_2D_ARRAY(Array_2D));
    PRINTF_d(sizeof(Array_3D));
    PRINTF_d(ELEMENTS_IN_3D_ARRAY(Array_3D));
    PRINTF_d(MATRICES_IN_3D_ARRAY(Array_3D));
    PRINTF_d(ROWS_IN_3D_ARRAY(Array_3D));
    PRINTF_d(COLUMNS_IN_3D_ARRAY(Array_3D));

    // Printing all elements in Array_3D using advertised macros
    // [
    int x, y, z;

    printf(
    "\nArray_3D[][][] Printed :\n"
    "----------------------------------------------\n");

    for(x = 0; x < MATRICES_IN_3D_ARRAY(Array_3D); x++)
    {
        for(y = 0; y < ROWS_IN_3D_ARRAY(Array_3D); y++)
        {
            for(z = 0; z < COLUMNS_IN_3D_ARRAY(Array_3D); z++)
                printf("%4.3i", Array_3D[x][y][z]);
            putchar('\n');
        }
        printf("---------------\n");
    }
    // ]

    // Applying those macros to solve the originally stated problem by Wickerman
    // [
    char result[10][7] = {
        {'1','X','2','X','2','1','1'},
        {'X','1','1','2','2','1','1'},
        {'X','1','1','2','2','1','1'},
        {'1','X','2','X','2','2','2'},
        {'1','X','1','X','1','X','2'},
        {'1','X','2','X','2','1','1'},
        {'1','X','2','2','1','X','1'},
        {'1','X','2','X','2','1','X'},
        {'1','1','1','X','2','2','1'},
        {'1','X','2','X','2','1','1'}
    };

    printf(
    "\nWickerman's problem solved :\n"
    "----------------------------------------------\n");
    PRINTF_d(sizeof(result)); // radha_SIZEOF_2D_ARRAY
    PRINTF_d(ELEMENTS_IN_2D_ARRAY(result)); // radha_SIZEOF_2D_ARRAY
    PRINTF_d(ROWS_IN_2D_ARRAY(result));
    PRINTF_d(COLUMNS_IN_2D_ARRAY(result));
    // ]
}
// ]
0
ShreeRadheKrishna
    // gets you the total size of the 2d array 
    printf("Arrays Total size: %ld\n",sizeof(result));

    // gets you the cumulative size of row which is 5 columns * sizeof(int)
    printf("1 row cumulative size: %ld\n",sizeof(result[0]));

    // division of total array size with cumulative size of row gets you total number of rows
    printf("total number of rows: %ld\n",sizeof(result)/sizeof(result[0]));

    // and total number of columns you get by dividing cumulative row size with sizeof(char)
    printf("total number of columns: %ld\n",sizeof(result[0])/sizeof(char));
0
mfaisal