2D array values C

Question

I wanted to declare a 2D array and assign values to it  without running a for loop   I thought I could used the following idea   int array 5     1 2 3 4 5     Which works fine to initialize the 2D array as well  But apparently my compiler doesn t like this       1   8  12  20  25  5   9  13  24  26      include  lt iostream h gt   int main         int arr 2  5     0        This actually initializes everything to 0      arr  1        1 8 12 20 25      Line 11     arr  2        5 9 13 24 26       return 0         J  CPP Grid bcc32 exe Grid cpp      Borland C   5 5 1 for Win32 Copyright  c  1993  2000 Borland      Grid cpp       Error E2188 Grid cpp 11  Expression syntax in function main        Error E2188 Grid cpp 12  Expression syntax in function main        Warning W8004 Grid cpp 14   arr  is assigned a value that is never used in funct   ion main          2 errors in Compile     Please help as to what is the right way to initialize the 2d array with my set of values

User · Answer

Just want to point out you do not need to specify all dimensions of the array.

The leftmost dimension can be 'guessed' by the compiler.

#include <stdio.h>
int main(void) {
  int arr[][5] = {{1,2,3,4,5}, {5,6,7,8,9}, {6,5,4,3,2}};
  printf("sizeof arr is %d bytes\n", (int)sizeof arr);
  printf("number of elements: %d\n", (int)(sizeof arr/sizeof arr[0]));
  return 0;
}

User · Answer

One alternative is to represent your 2D array as a 1D array   This can make element-wise operations more efficient   You should probably wrap it in a class that would also contain width and height   Another alternative is to represent a 2D array as an std  vector lt std  vector lt int gt   gt    This will let you use STL s algorithms for array arithmetic  and the vector will also take care of memory management for you

User · Answer

The proper way to initialize a multidimensional array in C or C   is  int arr 2  5      1 8 12 20 25    5 9 13 24 26      You can use this same trick to initialize even higher-dimensional arrays if you want   Also  be careful in your initial code - you were trying to use 1-indexed offsets into the array to initialize it   This didn t compile  but if it did it would cause problems because C arrays are 0-indexed

User · Answer

int iArray 2  2      1  2    3  4     Think of a 2D array as an array of arrays

User · Answer

Like this   int main         int arr 2  5                   1 8 12 20 25            5 9 13 24 26             This should be covered by your C   textbook  which one are you using   Anyway  better  consider using std  vector or some ready-made matrix class e g  from Boost

[c++] 2D array values C++

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