Conversion of string array to vector of string type

Question

I want to initialize a vector with following data of arr for that i have to initialize an array of string type and copy its value to vector string this is how i am doing it

it gives lots of errors

string arr[6][8]={
"AAAAAAAA",
"ABWBWBWA",
"ABWBWBWA",
"ABWBWBWA",
"ABWBWBWA",
"AAAAAAAA"};
vector<string> v(arr,arr+sizeof(arr)/sizeof(string));

I have done it for int array and vector of int type. Like this,

int vv[]={0,0,0,8};
vector<int> v(vv,vv+sizeof(vv)/sizeof(int));

and it works perfectly for this type but for string type its not working.

Kerrek SB · Accepted Answer · 2012-01-21 18:23:47Z

5

Your array makes no sense. It should be:

std::string arr[] = {
  "AAAAAAAA",
  "ABWBWBWA",
  "ABWBWBWA",
  "ABWBWBWA",
  "ABWBWBWA",
  "AAAAAAAA" };

Then

std::vector<std::string> v(arr, arr + sizeof(arr) / sizeof(std::string));

should work as expected.

Alternatively you can fix the 6 and say v(arr, arr + 6);.

In modern C++, however, you would just say,

std::vector<std::string> v {
  "AAAAAAAA",
  "ABWBWBWA",
  "ABWBWBWA",
  "ABWBWBWA",
  "ABWBWBWA",
  "AAAAAAAA"
};

answered Jan 21, 2012 at 18:23

Kerrek SB

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7 Comments

Md Faisal Over a year ago

can we do that in case of int type also?

Md Faisal Over a year ago

std::vector<std::string> v { "AAAAAAAA", "ABWBWBWA", "ABWBWBWA", "ABWBWBWA", "ABWBWBWA", "AAAAAAAA" };

Md Faisal Over a year ago

it says error: scalar object ‘v’ requires one element in initializer

Kerrek SB Over a year ago

@fsl4faisal: You need a modern compiler. In GCC, say -std=c++0x.

Md Faisal Over a year ago

cc1plus: error: unrecognized command line option "-std=c++0x"

|

Dietmar Kühl · Accepted Answer · 2012-01-21 19:18:09Z

The type of arr is actually not string but char[6][8] (it is odd this compiles because you are initializing the members of this array with char[9] objects: the string literals include a terminating '\0' character). To properly get the size of a statically size arrays I always recommend not to use this C hack of using sizeof(). Instead, use a function template like this (in fact, I just included the size() template because you used the size; using begin() and end() to get iterators is superior):

template <typename T, int Size> int size(T (&array)[Size]) { return Size; }
template <typename T, int Size> T* begin(T (&array)[Size]) { return array; }
template <typename T, int Size> T* end(T (&array)[Size])   { return array + Size; }
...
std::vector<std::string> v(begin(arr), end(arr));

In C++2011 begin() and end() functions are part of the standand C++ library. Of course, with C++2011 you could directly use initializer lists.

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