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How to Find the Mode of Numbers in an Array in C++?
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How to Find the Length of an Array in C++?

Last Updated : 29 Nov, 2024
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In C++, the length of an array is defined as the total number of elements present in the array. In this article, we will learn how to find the length of an array in C++.

The simplest way to find the length of an array is by using the sizeof operator. First calculate the size of the array in bytes and divide it by the size of the first element to get the length of the array. Let's take a look at an example:

C++ 
#include <bits/stdc++.h> using namespace std;  int main() {     int arr[] = {1, 2, 3, 4, 5};      // Finding the length of the array     int n = sizeof(arr) / sizeof(arr[0]);      cout << n;     return 0; }

Output
5

Note: Any of the method mentioned here cannot find the size of those array that are passed to the functions due to array decay in C++. That is why it is recommended to store and pass the size of the array using some variable.

Using Pointer Arithmetic

First get the pointer to the array by using & addressof operator on the array name and increment this pointer. Deference the obtained pointer and subtract the pointer to the first element of the array to get the size of the array.

C++ 
#include <bits/stdc++.h> using namespace std;  int main() {     int arr[5] = {1, 2, 3, 4, 5};      // Finding length of an array by using      // pointer arithmetic     cout << *(&arr + 1) - arr;      return 0; }

Output
5

Explanation: This trick works because of pointer arithmetic in C++. When an integer is added to a pointer, the compiler adjusts the address by multiplying the integer by the size of the data type the pointer points to.

In this case, we took a pointer to a given array arr and added 1 to it. When we add 1 to a pointer of an array, the compiler moves the pointer by the size of one whole array (not element). Subtracting the pointer to the first element from this pointer gives the array's length.

Using size() (Since C++17)

C++17 introduced the size() function, which can be used to get the number of elements in an array.

C++ 
#include <bits/stdc++.h> using namespace std;  int main() {     int arr[] = {1, 2, 3, 4, 5};      	// Finding the size of array arr     int n = size(arr);        cout << n;     return 0; }


Output

5



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How to Find the Mode of Numbers in an Array in C++?

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