Check out example codes for "find index of element in vector c++". It will help you in understanding the concepts better.

Code Example 1

// C++ program to find the index 
// of an element in a vector 
  
#include <bits/stdc++.h> 
using namespace std; 
  
// Function to print the 
// index of an element 
void getIndex(vector<int> v, int K) 
{ 
    auto it = find(v.begin(), v.end(), K); // returns iterator to element K 
  
    // If element was found 
    if (it != v.end()) { 
        // calculating the index 
        // of K 
        int index = distance(v.begin(), it); 
        cout << index << endl; 
    } 
    else { 
        // If the element is not 
        // present in the vector 
        cout << "-1" << endl; 
    } 
} 
// Driver Code 
int main() 
{ 
    // Vector 
    vector<int> v = { 1, 45, 54, 71, 76, 17 }; 
    // Value whose index 
    // needs to be found 
    int K = 54; 
    getIndex(v, K); 
    return 0; 
}

Code Example 2

// CPP program to illustrate  
// std::find 
// CPP program to illustrate  
// std::find 
#include<bits/stdc++.h> 
  
int main () 
{ 
    std::vector<int> vec { 10, 20, 30, 40 }; 
      
    // Iterator used to store the position  
    // of searched element 
    std::vector<int>::iterator it; 
      
    // Print Original Vector 
    std::cout << "Original vector :"; 
    for (int i=0; i<vec.size(); i++) 
        std::cout << " " << vec[i]; 
          
    std::cout << "\n"; 
      
    // Element to be searched 
    int ser = 30; 
      
    // std::find function call 
    it = std::find (vec.begin(), vec.end(), ser); 
    if (it != vec.end()) 
    { 
        std::cout << "Element " << ser <<" found at position : " ; 
        std::cout << it - vec.begin() << " (counting from zero) \n" ; 
    } 
    else
        std::cout << "Element not found.\n\n"; 
          
    return 0; 
}

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