# Find index of an element in a Set in C++

Given a set **S** consisting of **N** integers and an element **K**, the task is to find the index of the element **K** in the set **S**. If the element is not present in **S**, print **-1**.

**Examples:**

Input:N = 5, S = {1, 2, 3, 4, 6} K = 6Output:5Explanation:6 is the 5th element in S.

Input:N = 5, S = {1, 2, 3, 4, 6}, K = 5Output:-1Explanation:5 is not present in this set so we give output as -1.

**Approach: **Follow the steps below to solve the problem:

- Initialize a variable, say
**index**as**1**, to store the index of the required element. - Traverse the set
**S**and perform the following operations: - If the current element is
**K**, print**Index**and break out of the loop. - Otherwise, increment
**Index.**

Below is the implementation of the above approach:

## C++

`// C++ program to implement` `// the above approach` `#include <bits/stdc++.h>` `using` `namespace` `std;` `// Function to calculate index` `// of element in a Set` `int` `GetIndex(set<` `int` `> S, ` `int` `K)` `{` ` ` `// To store the index of K` ` ` `int` `Index = 1;` ` ` `// Traverse the Set` ` ` `for` `(` `auto` `u : S) {` ` ` `if` `(u == K)` ` ` `return` `Index;` ` ` `Index++;` ` ` `}` ` ` `// If K is not present` ` ` `// in the set` ` ` `return` `-1;` `}` `// Driver Code` `int` `main()` `{` ` ` `// Input` ` ` `set<` `int` `> S;` ` ` `S.insert(1);` ` ` `S.insert(6);` ` ` `S.insert(2);` ` ` `S.insert(3);` ` ` `S.insert(4);` ` ` `int` `K = 6;` ` ` `cout << GetIndex(S, K) << endl;` ` ` `return` `0;` `}` |

**Output:**

5

**Time Complexity**: O(N)**Auxiliary Space:** O(1)

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