Finding index of an array element??

[Raza5680]

Hi, Is there any function that returns an index of a particular element in a numeric array. Thanks P.S. I am looking for an equivalent of MATLAB's find() function.

[Nuri Ismail]

You can use a combination of std::find[^] and std::distance[^] in order to search for an element and get its index. The standard algorithms will work both on standard containers and arrays. Here is a quick example for you, which demonstrates the usage of std::find and std::distance with std::vector and regular array:

    // Prepare the test array
int arr\[\] = {31, 53, 7, 9, 45, 20};
const int size = (sizeof(arr) / sizeof(arr\[0\]));
int\* arr\_beg = arr;
int\* arr\_end = arr + size;

// Prepare the test vector
std::vector<int> vec;
std::copy(arr, arr + size, std::back\_inserter(vec));

// Search the array
std::cout << "\\n Searching the array for element with value 7...";
int\* res1 = std::find(arr, arr + size, 7);
if(res1 != arr\_end)
    std::cout << "\\n The element is found at index: " << std::distance(arr\_beg, res1);
else
    std::cout << "\\n The element is not found";

std::cout << "\\n Searching the array for element with value 8...";
int\* res2 = std::find(arr, arr + size, 8);
if(res2 != arr\_end)
        std::cout << "\\n The element is found at index: " << std::distance(arr\_beg, res2);
else
    std::cout << "\\n The element is not found";


// Search the vector
std::cout << "\\n Searching the vector for element with value 7...";
std::vector<int>::iterator it1 = std::find(vec.begin(), vec.end(), 7);
if(it1 != vec.end())
    std::cout << "\\n The element is found at index: " << std::distance(vec.begin(), it1);
else
    std::cout << "\\n The element is not found";

std::cout << "\\n Searching the vector for element with value 8...";
std::vector<int>::iterator it2 = std::find(vec.begin(), vec.end(), 8);
if(it2 != vec.end())
    std::cout << "\\n The element is found at index: " << std::distance(vec.begin(), it2);
else
    std::cout << "\\n The element is not found";

I hope this helps. :)

[jk chan]

you can use std::find function.you need to include algorithm header file for example if you have a vector containing some integers you can call it like this vector::iterator the_index = std::find( vcNumbers.begin(),vcNumbers.end(), number_to_search ); you can check if the index is valid by checking it against vcNumers.end().Something like this. if( vcNumbers.end() != the_index) cout << *it; hopes this helps :)

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