C++ program to get the last element in an array

Store multiple elements of the same type in a location where they can be accessed sequentially or in a way that allows sequential access. Arrays are one of the best options. In almost any computer language, arrays or related data structures can be used to store data. Arrays are linear data structures because basic operations such as insertion, deletion, traversal, and update take linear time to complete. Accessing array items is also simple. This article will demonstrate how to select the last element in a C array.

Understand concepts and illustrate with examples

Given array A = [10, 14, 65, 85, 96, 12, 35, 74, 69]
The last element is 69

For example, the last member can be accessed using the index position, as in the array given in the previous example. In C (and other programming languages ​​like Java and Python), array indexing starts at index 0. So, to read the last index, we just select the element from index (n − 1), where n is the element count of the array.

algorithm

• Take an array A as input

• n := The number of elements in A

• last_element := Use A[ n – 1 ] to get

• Return the last element

The Chinese translation of

Example

is:

Example

#include <iostream>
# define Z 50

using namespace std;

void displayArr(int arr[], int n){
   for( int i = 0; i < n; i++ ){
      cout << arr[ i ] << ", ";
   }
   cout << endl;
}

int pickLastElement( int A[], int n) {
   int last;
   last = A[ n - 1 ];
   return last;
}

int main() {
   int A[ Z ] = {57, 10, 14, 19, 86, 52, 32, 14, 76, 65, 32, 14};
   int n = 12;
   
   cout << "Given Array: ";
   displayArr( A, n );
   
   int last = pickLastElement( A, n ); 
   cout << "The last element of A: " << last << endl;
   
   int B[ Z ] = { 98, 12, 10, 23, 45, 74 };
   int m = 6;
   
   cout << "Another array: ";
   displayArr( B, m );
   
   last = pickLastElement( B, m ); 
   cout << "The last element of B: " << last << endl;
}

Output

Given Array: 57, 10, 14, 19, 86, 52, 32, 14, 76, 65, 32, 14, 
The last element of A: 14
Another array: 98, 12, 10, 23, 45, 74, 
The last element of B: 74

Using pointers and base addresses

The array is the location address of the base address (first) plus the offset (indices). Therefore, you can use pointers to access the index without using square brackets. To get the last element, you can use the base address value of the array. Let's look at the concrete implementation to get a clearer view.

The Chinese translation of

Example

is:

Example

#include <iostream>
# define Z 50

using namespace std;

void displayArr(int arr[], int n){
   for( int i = 0; i < n; i++ ){
      cout << arr[ i ] << ", ";
   }
   cout << endl;
}

int pickLastElement( int A[], int n) {
   int last;
   last = *(A + n - 1);
   return last;
}

int main() {
   int A[ Z ] = {57, 10, 14, 19, 86, 52, 32, 14, 76, 65, 32, 14};
   int n = 12;
   
   cout << "Given Array: ";
   displayArr( A, n );
   
   int last = pickLastElement( A, n ); 
   cout << "The last element of A: " << last << endl;
   
   int B[ Z ] = { 98, 12, 10, 23, 45, 74 };
   int m = 6;
   
   cout << "Another array: ";
   displayArr( B, m );
   
   last = pickLastElement( B, m ); 
   cout << "The last element of B: " << last << endl;
}

Output

Given Array: 57, 10, 14, 19, 86, 52, 32, 14, 76, 65, 32, 14, 
The last element of A: 14
Another array: 98, 12, 10, 23, 45, 74, 
The last element of B: 74

The value of A here (represented by pointer *A) represents the value of the address pointed to by A. This is the base address of the array.

Use vectors

Vectors are dynamic arrays, otherwise, the whole thing is array-like. Here, to read the last element, we only need to access the last index, which is vector.size() - 1. The code is as follows -

The Chinese translation of

Example

is:

Example

#include <iostream>
#include <vector>
# define Z 50

using namespace std;

void displayArr( vector<int> v ){
   for( int i = 0; i < v.size() ; i++ ){
      cout << v[ i ] << ", ";
   }
   cout << endl;
} 

int pickLastElement( vector<int> A) {
   int last;
   last = A[ A.size() - 1 ];
   return last;
}

int main() {
   vector<int> A = {57, 10, 14, 19, 86, 52, 32, 14, 76, 65, 32, 14};
   
   cout << "Given Array: ";
   displayArr( A );
   
   int last = pickLastElement( A ); 
   cout << "The last element of A: " << last << endl;
   
   vector<int> B = { 98, 12, 10, 23, 45, 74 };
   
   cout << "Another array: ";
   displayArr( B );
   
   last = pickLastElement( B ); 
   cout << "The last element of B: " << last << endl;
}

Output

Given Array: 57, 10, 14, 19, 86, 52, 32, 14, 76, 65, 32, 14, 
The last element of A: 14
Another array: 98, 12, 10, 23, 45, 74, 
The last element of B: 74

Using the vector's back() function

In the previous method we used index 0 to get the element, but there is another possible way. We can use the back() method to return the last element. Let's take a look at the code to get a clearer view.

The Chinese translation of

Example

is:

Example

#include <iostream>
#include <vector>
# define Z 50

using namespace std;

void displayArr( vector<int> v ){
   for( int i = 0; i < v.size() ; i++ ){
      cout << v[ i ] << ", ";
   }
   cout << endl;
} 

int pickLastElement( vector<int> A) {
   int last;
   last = A.back();
   return last;
}

int main() {
   vector<int> A = {57, 10, 14, 19, 86, 52, 32, 14, 76, 65, 32, 14};
   
   cout << "Given Array: ";
   displayArr( A );
   
   int last = pickLastElement( A ); 
   cout << "The last element of A: " << last << endl;
   
   vector<int> B = { 98, 12, 10, 23, 45, 74 };
   
   cout << "Another array: ";
   displayArr( B );
   
   last = pickLastElement( B ); 
   cout << "The last element of B: " << last << endl;
}

Output

Given Array: 57, 10, 14, 19, 86, 52, 32, 14, 76, 65, 32, 14, 
The last element of A: 14
Another array: 98, 12, 10, 23, 45, 74, 
The last element of B: 74

in conclusion

We have seen four different methods for reading the last element from an array. The first two methods are implemented based on static arrays in C. To read the last element, we just need to take the element from index 0. The same operation can be accomplished using the base address pointer of the array. The base address points to the first block, the value at that index will be the first element and by adding the offset we get the last element. In the next two methods, we use vectors. The approach here is the same as for static arrays. The last method uses the vector iterator's back() function, which returns the last element in the vector.

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