how to find 2d array size in c

Question

How do I find the size of a 2D array in C    Is there any predefined function like sizeof to determine the size of the array   Also  can anyone tell me how to detect an error in the getvalue method for arrays while trying to get a value which is not set

User · Answer

Use an std  vector   std  vector lt  std  vector lt int gt   gt  my array     2D Array     my array size       size of y    my array 0  size       size of x      Or  if you can only use a good ol  array  you can use sizeof   sizeof  my array       y size    sizeof  my array 0        x size

User · Answer

include  lt bits stdc   h gt  using namespace std    int main int argc  char const  argv          int arr 6  5               1 2 3 4 5            1 2 3 4 5            1 2 3 4 5            1 2 3 4 5            1 2 3 4 5            1 2 3 4 5             int rows   sizeof arr  sizeof arr 0        int cols   sizeof arr 0   sizeof arr 0  0        cout lt  lt rows lt  lt     lt  lt cols lt  lt endl      return 0      Output  6 5

User · Answer

int arr 5  4    For the row subscript 4 raise to 2  include cmath to use pow     sizeof arr1  pow 4 2       Column subscript   sizeof  arr1  4   4 means 4 bytes  size of int

User · Answer

The other answers above have answered your first question  As for your second question  how to detect an error of getting a value that is not set  I am not sure which of the following situation you mean    Accessing an array element using an invalid index  If you use std  vector  you can use vector  at function instead of    operator to get the value  if the index is invalid  an out of range exception will be thrown  Accessing a valid index  but the element has not been set yet  As far as I know  there is no direct way of it  However  the following common practices can probably solve you problem   1  Initializes all elements to a value that you are certain that is impossible to have  For example  if you are dealing with positive integers  set all elements to -1  so you know the value is not set yet when you     find it being -1     2   Simply use a bool array of the same size to     indicate whether the element of the same index is set or not  this     applies when all values are  possible

User · Answer

Here is one possible solution of first part   include lt iostream gt   using namespace std  int main         int marks   4                            10  20  30  50                        40  50  60  60                        10  20  10  70                          int rows    sizeof marks  sizeof marks 0    int cols   sizeof marks   sizeof int  rows         for int i 0  i lt rows  i                  for int j 0  j lt cols  j                          cout lt  lt marks i  j  lt  lt                        cout lt  lt endl               return 0

User · Answer

Along with the  countof   macro you can refer to the array size using pointer notation  where the array name by itself refers to the row  the indirection operator appended by the array name refers to the column     include  lt iostream gt   include  lt iomanip gt   using namespace std   int main         int beans 3  4             1  2  3  4               5  6  7  8               9  10  11  12               cout  lt  lt   Row size      lt  lt   countof beans      Output row size          lt  lt    nColumn size      lt  lt   countof  beans       Output column size     cout  lt  lt  endl          Used in a for loop with a pointer       int  pbeans  4   beans         for  int i    i  lt   countof beans     i             cout  lt  lt  endl           for  int j    j  lt   countof  beans     j                 cout  lt  lt  setw 4   lt  lt  pbeans i  j                         cout  lt  lt  endl

User · Answer

include lt iostream gt  using namespace std   int main         int A 3  4       1 2 3 4     4 5 7 8     9 10 11 12          for int rows 0   rows lt sizeof A  sizeof  A    rows                  for int columns 0   columns lt  sizeof  A    sizeof  A 0     columns                          cout lt  lt A rows  columns   lt  lt   t                      cout lt  lt endl

User · Answer

sizeof yourObj  sizeOf yourObj 0     should do the trick

User · Answer

Suppose you were only allowed to use array then you could find the size of 2-d array by the following way     int ary   5       1  2  3  4  5                       6  7  8  9  0                         int rows    sizeof ary   sizeof ary 0      2 rows      int cols   sizeof ary 0    sizeof int      5 cols

[c++] how to find 2d array size in c++

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