Array algorithms in C++ STL (all_of, any_of, none_of, copy_n and iota)
Last Updated :
25 Oct, 2022
From C++11 onwards, some new and interesting algorithms are added in STL of C++. These algorithms operate on an array and are useful in saving time during coding and hence useful in competitive programming as well.
all_of() This function operates on whole range of array elements and can save time to run a loop to check each elements one by one. It checks for a given property on every element and returns true when each element in range satisfies specified property, else returns false.
CPP
// C++ code to demonstrate working of all_of()
#include<iostream>
#include<algorithm> // for all_of()
using namespace std;
int main()
{
// Initializing array
int ar[6] = {1, 2, 3, 4, 5, -6};
// Checking if all elements are positive
all_of(ar, ar+6, [](int x) { return x>0; })?
cout << "All are positive elements" :
cout << "All are not positive elements";
return 0;
}
Output:
All are not positive elements
Time Complexity: O(n)
Auxiliary Space: O(1)
In the above code, -6 being a negative element negates the condition and returns false.
any_of() This function checks for a given range if there's even one element satisfying a given property mentioned in function. Returns true if at least one element satisfies the property else returns false.
CPP
// C++ code to demonstrate working of any_of()
#include<iostream>
#include<algorithm> // for any_of()
using namespace std;
int main()
{
// Initializing array
int ar[6] = {1, 2, 3, 4, 5, -6};
// Checking if any element is negative
any_of(ar, ar+6, [](int x){ return x<0; })?
cout << "There exists a negative element" :
cout << "All are positive elements";
return 0;
}
Output:
There exists a negative element
Time Complexity: O(n)
Auxiliary Space: O(1)
In above code, -6 makes the condition positive.
none_of() This function returns true if none of elements satisfies the given condition else returns false.
CPP
// C++ code to demonstrate working of none_of()
#include<iostream>
#include<algorithm> // for none_of()
using namespace std;
int main()
{
// Initializing array
int ar[6] = {1, 2, 3, 4, 5, 6};
// Checking if no element is negative
none_of(ar, ar+6, [](int x){ return x<0; })?
cout << "No negative elements" :
cout << "There are negative elements";
return 0;
}
Output:
No negative elements
Time Complexity: O(n)
Auxiliary Space: O(1)
Since all elements are positive, the function returns true.
copy_n() copy_n() copies one array elements to new array. This type of copy creates a deep copy of array. This function takes 3 arguments, source array name, size of array and the target array name.
CPP
// C++ code to demonstrate working of copy_n()
#include<iostream>
#include<algorithm> // for copy_n()
using namespace std;
int main()
{
// Initializing array
int ar[6] = {1, 2, 3, 4, 5, 6};
// Declaring second array
int ar1[6];
// Using copy_n() to copy contents
copy_n(ar, 6, ar1);
// Displaying the copied array
cout << "The new array after copying is : ";
for (int i=0; i<6 ; i++)
cout << ar1[i] << " ";
return 0;
}
Output:
The new array after copying is : 1 2 3 4 5 6
Time Complexity: O(n)
Auxiliary Space: O(n)
In the above code, the elements of ar are copied in ar1 using copy_n()
iota() This function is used to assign continuous values to array. This function accepts 3 arguments, the array name, size, and the starting number.
CPP
// C++ code to demonstrate working of iota()
#include<iostream>
#include<numeric> // for iota()
using namespace std;
int main()
{
// Initializing array with 0 values
int ar[6] = {0};
// Using iota() to assign values
iota(ar, ar+6, 20);
// Displaying the new array
cout << "The new array after assigning values is : ";
for (int i=0; i<6 ; i++)
cout << ar[i] << " ";
return 0;
}
Output:
The new array after assigning values is : 20 21 22 23 24 25
Time Complexity: O(n)
Auxiliary Space: O(1)
In the above code, continuous values are assigned to array using iota().
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