Array algorithms in C++ STL (all_of, any_of, none_of, copy_n and iota)
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.
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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
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
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.
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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
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().
