2D array of chars to 1D array of strings

Question

what is the easiest way to copy a two-dimensional array of chars into a one-dimensional array of strings in c++?

something like that:

    char inCharArray[3][255];
    string outStringArray[3];

    for (int i = 0; i < sizeof(inCharArray) / sizeof(inCharArray[i]); i++)
    {
        outStringArray[i] = inCharArray[i];
    }

Regards Tillman

/*const*/std::string outStringArray[3]{inCharArray[0], inCharArray[1], inCharArray[2]};? — Jarod42
– Jarod42, Commented Mar 15, 2021 at 14:19
/*const*/ std::vector<std::string> outStringArray(std::begin(inCharArray), std::end(inCharArray));? — Jarod42
– Jarod42, Commented Mar 15, 2021 at 14:19
std::copy(std::begin(inCharArray), std::end(inCharArray), std::begin(outStringArray));? — Jarod42
– Jarod42, Commented Mar 15, 2021 at 14:22
These assume C-strings. While a C-string is always an array of characters, the inverse is not always true. OP should clarify. — sweenish
– sweenish, Commented Mar 15, 2021 at 14:24
I love how OP was asked specifically about inCharArray and answered with outStringArray. Classic. — sweenish
– sweenish, Commented Mar 15, 2021 at 15:00

Guillaume Racicot · Accepted Answer · 2021-03-15 14:24:37Z

1

Using STL algorithm is one of the best way to do it.

char inCharArray[3][255];
string outStringArray[3];

std::transform(
    std::begin(inCharrArray),
    std::end(inCharArray),
    std::begin(outStringArray),
    [](char const* c_str) -> std::string {
        return std::string{c_str};
    }
);

This is assuming the strings are ending sooner than 255.

answered Mar 15, 2021 at 14:24

Guillaume Racicot

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Comments

Woodford · Accepted Answer · 2021-03-15 18:33:40Z

0

This alternative to std::transform is more readable to me:

std::copy(std::begin(inCharArray),
          std::end(inCharArray),
          std::begin(outStringArray));

// only safe if input strings are null-terminated and arrays have equal size
static_assert(std::size(inCharArray) == std::size(outStringArray),
              "arrays are not equal size");

Also consider using std::array instead of C-style arrays while you're writing C++ code.

edited Mar 15, 2021 at 18:33

answered Mar 15, 2021 at 18:23

Woodford

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