C++ Program to Find Index of First Occurrence of a Value in Array

In C++, an array is a data structure that stores elements of the same type in contiguous memory locations. In this article, we will learn how to find the index of the first occurrence of a specific value in an array in C++.

Example:

Input: 
int arr[] = {5, 7, 1, 2, 3, 7, 1} 
Target = 1
Output: 
The first occurrence of 1 is at index: 2

Finding the Index of the First Occurrence of an Element in an Array

To find the index of the first occurrence of a value in an array, we can simply use a loop to iterate through the array and check if the element matches with the target if it matches return the index that is the first occurrence of a value in an array.

C++ Program to Find the Index of the First Occurrence of a Value in an Array 

The below example demonstrates the use of a for loop to find the index of the first occurrence of a value in a given array in C++.

// C++ Program to show how to Find the Index of the First Occurrence of // a Value in an Array #include <iostream> using namespace std; int main() {  // initializing array  int arr[] = { 5, 7, 1, 2, 3, 7, 1 };  int n = sizeof(arr) / sizeof(arr[0]);  // target whose first occurence need to be searched  int target = 1;  int index = -1;  // using a for loop to find the first occurrence of  // the element in the array.  for (int i = 0; i < n; i++) {  if (arr[i] == target) {  index = i;  break;  }  }  // if target is found print it's index  if (index != -1) {  cout << "The first occurrence of " << target  << " is at index: " << index << endl;  }  // else element not found  else {  cout << "Element not found." << endl;  }  return 0; } 

The first occurrence of 1 is at index: 2 

Time Complexity: O(N), here N is the number of elements in the array.
Auxiliary Space: O(1)