C++ 2 dimensional array with variable size rows

With C++11, you can do it easily with vectors (line breakes added for readability):

std::vector< std::vector <int > > arr = {{1,2,3},{4,5},{6,7,8,9,0}};

If you don't have a C++11 compiler, it works the exact same way, but you will not be able to initialize them as easy. You can set elements individually:

std::vector< std::vector <int > > arr;//vector of vectors. Think of each element as of a "row"std::vector<int> sub;//a temporary "row"sub.push_back(1);sub.push_back(2);arr.push_back(sub);//Adding a "row" to the vectorsub.clear();//Making another onesub.push_back(1);sub.push_back(12);sub.push_back(54);arr.push_back(sub);//Adding another "row" to the vector

Or you can initialize each "row" with an ordinary array:

std::vector< std::vector <int > > arr;static const int arr[] = {1,2,3,4};//A "row" as an ordinary arrayvector<int> vec (arr, arr + sizeof(arr) / sizeof(arr[0]) ); //Setting a "Row" as a vectorarr.push_back(vec);//Adding the "row" to the vector of vectors. 

It's not exactly possible to do what you want with ordinary arrays, since when you make an array[X][Y], it automaticaly is an X*Y matrix. You could, however, use an array of pointers:

int * array[3];//also possible: int ** array =  new int*[3]; but don't forget to delete it afterwards.int sub1[3] = {1,2,3};int sub2[2] = {1,2};int sub3[4] = {1,2,3,4};array[0] = sub1;array[1] = sub2;array[2] = sub3;

and access elements with array[X][Y]. However, the vector solution is much better overall.

You can do it like this (assuming an array of int elements):

int** arr = new int*[5];for(size_t i = 0; i < 5; ++i){    arr[i] = new int[4];}

and this gives you a two-dimensional dynamically allocated array of 5 by 4. You can then use it like this: arr[i][j] = 15;

Do not forget to de-allocate the memory after you are done using the array:

for(size_t i = 0; i < 5; ++i){    delete[] arr[i];}delete[] arr;

I would recommend using std::vector, however. You can see the other answers for reference.

A way for different row size

#include <iostream>#include <string>int main(){  int test1[]={1,2,3};  int test2[]={4,5};  int *test[]={test1,test2};  std::cout << test[0][1];//2  std::cout << test[1][1];//5}