array::at() in C++ STL
Last Updated :
19 Jan, 2018
Array classes are generally more efficient, light-weight and reliable than C-style arrays. The introduction of array class from C++11 has offered a better alternative for C-style arrays.
array::at()
This function is used to return the reference to the element present at the position given as the parameter to the function.
Syntax:
array_name.at(position)
Parameters:
Position of the element to be fetched.
Return: It return the reference to the element at the given position.
Examples:
Input: array_name1 = [1, 2, 3]
array_name1.at(2);
Output: 3
Input: array_name2 = ['a', 'b', 'c', 'd', 'e']
array_name2.at(4);
Output: e
#include <bits/stdc++.h>
using namespace std;
int main()
{
array< int , 3> array_name1;
array< char , 5> array_name2;
for ( int i = 0; i < 3; i++)
array_name1[i] = i+1;
for ( int i = 0; i < 5; i++)
array_name2[i] = 97+i;
cout << "Element present at position 2: "
<< array_name1.at(2) << endl;
cout << "Element present at position 4: "
<< array_name2.at(4);
return 0;
}
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Output:
Element present at position 2: 3
Element present at position 4: e
Time Complexity: Constant i.e. O(1).
Application:
Given an array of integers, print integers in alternate fashion starting from 1st position.
Input: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
Output: 2 4 6 8 10
#include <bits/stdc++.h>
using namespace std;
int main()
{
array< int , 10> a;
for ( int i = 0; i < 10; i++)
a[i] = i+1;
for ( int i = 0; i < a.size(); ++i) {
if (i % 2 != 0) {
cout << a.at(i);
cout << " " ;
}
}
return 0;
}
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Output:
2 4 6 8 10
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