# Working with Array and Vectors using STL in C++

Last Updated : 13 Mar, 2023

Using STL library it is very easy to perform certain basic operations on array like Sorting, searching, sum of elements, finding minimum and maximum element of the array.

Sorting

Sorting can be done with the help of sort() function. sort(starting_index, last_index) â€“ To sort the given array/vector. The sort() function works on quick sort algorithm. C++ STL provides a similar function sort that sorts a vector or array (items with random access). The time complexity of this function is O(nlogn). Example:

```Input: {1, 7, 2, 4, 8, 3}
Output: {1, 2, 3, 4, 7, 8}```

## Array

 `// C++ program to sort Array` `// using sort() in STL`   `#include ` `using` `namespace` `std;`   `int` `main()` `{` `    ``int` `a[] = { 1, 7, 2, 4, 8, 3 };` `    ``int` `l = ``sizeof``(a) / ``sizeof``(a[0]);` `    ``sort(a, a + l);` `    ``for` `(``int` `i; i < l; i++)` `        ``cout << a[i] << ``" "``;` `    ``return` `0;` `}`

## Vector

 `// C++ program to sort Vector` `// using sort() in STL`   `#include ` `using` `namespace` `std;`   `int` `main()` `{` `    ``vector<``int``> a = { 1, 7, 2, 4, 8, 3 };` `    ``sort(a.begin(), a.end());` `    ``for` `(``int` `i; i < a.size(); i++)` `        ``cout << a[i] << ``" "``;` `    ``return` `0;` `}`

Output

`1 2 3 4 7 8 `

Reverse

Reversing can be done with the help of reverse() function. reverse(start_index, last_index): To reverse the given array/vector. Example:

```Input: {1, 7, 2, 4, 8, 3}
Output: {3, 8, 4, 2, 7, 1}```

## Array

 `// C++ program to reverse Array` `// using reverse() in STL`   `#include ` `using` `namespace` `std;`   `int` `main()` `{` `    ``int` `a[] = { 1, 7, 2, 4, 8, 3 };` `    ``int` `l = ``sizeof``(a) / ``sizeof``(a[0]);` `    ``reverse(a, a + l);` `    ``for` `(``int` `i = 0; i < l; i++)` `        ``cout << a[i] << ``" "``;` `    ``return` `0;` `}`

## Vector

 `// C++ program to reverse Vector` `// using reverse() in STL`   `#include ` `using` `namespace` `std;`   `int` `main()` `{` `    ``vector<``int``> a = { 1, 7, 2, 4, 8, 3 };` `    ``reverse(a.begin(), a.end());` `    ``for` `(``int` `i; i < a.size(); i++)` `        ``cout << a[i] << ``" "``;` `    ``return` `0;` `}`

Output

`3 8 4 2 7 1 `

Finding Sum, Maximum and Minimum element

The functions in STL to do the mentioned works are:

• accumulate(first_index, last_index, initial value of sum): This function returns the sum of all elements of a array/vector.
• *max_element (first_index, last_index): To find the maximum element of a array/vector.
• *min_element (first_index, last_index): To find the minimum element of a array/vector.

## Array

 `// C++ program to find sum, max and min` `// element of Array using STL`   `#include ` `using` `namespace` `std;`   `int` `main()` `{` `    ``int` `a[] = { 1, 7, 2, 4, 8, 3 };` `    ``int` `l = ``sizeof``(a) / ``sizeof``(a[0]);` `    ``cout << ``"\nsum of array: "` `         ``<< accumulate(a, a + l, 0);` `    ``cout << ``"\nMaximum element in array: "` `         ``<< *max_element(a, a + l);` `    ``cout << ``"\nMinimum element in array: "` `         ``<< *min_element(a, a + l);` `    ``return` `0;` `}`

## Vector

 `// C++ program to find sum, max and min` `// element of Vector using STL`   `#include ` `using` `namespace` `std;`   `int` `main()` `{` `    ``vector<``int``> a = { 1, 7, 2, 4, 8, 3 };` `    ``cout << ``"\nsum of vector: "` `         ``<< accumulate(a.begin(), a.end(), 0);` `    ``cout << ``"\nMaximum element in vector: "` `         ``<< *max_element(a.begin(), a.end());` `    ``cout << ``"\nMinimum element in vector: "` `         ``<< *min_element(a.begin(), a.end());` `    ``return` `0;` `}`

Output

```sum of array: 25
Maximum element in array: 8
Minimum element in array: 1```

Count

Count STL function is used to count the number of occurrences of a particular element in an array and a vector. This can be done with help of count() function,
count (startindex , last index , element).
Example:

## C++

 `// C++ program to count no. of occurrence of element in an Array and Vector` `// using count()`   `#include ` `using` `namespace` `std;`   `int` `main()` `{   ` `    ``//implementation of count in array` `    ``// sample array` `    ``int` `arr[] = {1, 2, 3, 4, 5, 4, 3, 2, 1}; `   `    ``// size of the array` `    ``int` `n = ``sizeof``(arr) / ``sizeof``(arr[0]); `   `    ``// count number of occurrences of 4 in the array` `    ``int` `count1 = count(arr, arr + n, 4); `   `    ``cout << ``"Number of occurrences of 4 in the array: "` `<< count1 << endl;`     `    ``//implementation of count in vector` `    ``vector<``int``> vec{1, 2, 3, 4, 5, 5, 5, 5, 6, 7, 8, 9, 10};`   `    ``// Count the number of occurrences of the element 5` `    ``int` `count2 = count(vec.begin(), vec.end(), 5);`   `    ``cout << ``"Number of occurrences of 5 in vector: "` `<< count2 <

Output

```Number of occurrences of 4 in the array: 2
Number of occurrences of 5 in vector: 4```

Find

Find can be done with help of find() function, find (start index , last index , element). This function is used to search for a specific element in an array and a vector. Example:

## C++

 `// C++ program to find element in Array and vector` `// using find() function`   `#include ` `using` `namespace` `std;`   `int` `main() {` `    ``int` `arr[] = {1, 2, 3, 4, 5};` `    ``int` `size = ``sizeof``(arr) / ``sizeof``(arr[0]);` `    ``int` `key = 3;`   `    ``// Find the element in the array` `    ``int``* ptr = find(arr, arr + size, key);`   `    ``// If the element is found` `    ``if` `(ptr != arr + size) {` `        ``cout << ``"Element found in array at position "` `                  ``<< (ptr - arr) << endl;` `    ``} ` `   ``// If the element is not found` `    ``else` `{` `        ``cout << ``"Element not found in array"` `<< endl;` `    ``}`   `    ``// Implementation of find() in vector`   `    ``// Create a vector of integers` `    ``vector<``int``> vec = {1, 2, 3, 4, 5};`   `    ``// Find the first occurrence of 4 in the vector` `    ``auto` `it = find(vec.begin(), vec.end(), 4);`   `    ``// If the element is found` `    ``if` `(it != vec.end())` `    ``{` `        ``cout << ``"Element found in vector at index "` `<< distance(vec.begin(), it) << endl;` `    ``}` `    ``// If the element is not found` `    ``else` `    ``{` `        ``cout << ``"Element not found in vector"` `<< endl;` `    ``}`   `    ``return` `0;` `}`   `//This code is contributed by akashjha412`

Output

```Element found in array at position 2
Element found in vector at index 2```

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