# Second Largest/Smallest Number in Array in C/C++, Java and Python

In an earlier tutorial, we have seen how to find the smallest or largest number from the integer array. In this tutorial, we are going to find the second smallest number in an array **in a single iteration**.

**Input:**

- integer array

**Output:**

- Print second smallest integer in given array.

We can easily find the second smallest number by traversing the array twice. In the first traversing, find the first smallest number. And in second traversing find the second smallest number. But this is not the optimal solution to the problem.

Finding second smallest number in array with single iteration is a bit tricky. Here is the algorithm to solve this problem.

This question was asked in the Goldman Sachs coderpad online interview.

Table of Contents

#### Algorithm

- Compare the first two elements from the array.
- Initialize the
`small_first`

with the smallest number. - Initialize the
`small_second`

with the smallest number.

- Initialize the
- Loop over internet array from 3rd number.
- If the current number is smaller than small_first
- assign small_first to small_second
- assign a current number to small_first

- If the current number is smaller than small_first
- Print small_second.

If you understand the logic from the above algorithm, you can solve the problem in any programming language. Let’s implement this algorithm in different programming languages.

**Note:** By changing some conditional statements, you can also implement the program to find the **second largest number in the given array**. That is just another story. Let’s stick with the original problem first.

#### C/C++ Program

**Prerequisites:**

**C/C++ Code:**

#include <stdio.h> int main() { //initialize array int arr[7] = {34, 62, 56, 13, 7, 9, 17}; int i=0; int small_first = arr[0]; int small_second = arr[0]; //initializ first and second smallest number if(arr[0] > arr[1]) { small_first = arr[1]; small_second = arr[0]; } else { small_first = arr[0]; small_second = arr[1]; } for(i = 2; i < 7; i++) { //compare smallest number with current number if(arr[i]<=small_first) { small_second = small_first; small_first = arr[i]; } else if(arr[i]<small_second){ small_second = arr[i]; } } //print second smallest number from array printf("Second smallest number in array is %d.", small_second); return 0; }

**Output:**

Second smallest number in array is 9.

#### Java Program

Prerequisites:

**Java Code:**

public class Smallest_Largest_Element_Array { public static void main(String[] args) { // initialize the array int [] arr = new int [] {67, 83, 8, 71, 29, 3, 48}; int small_first = arr[0]; int small_second = arr[0]; //initializ first and second smallest number if(arr[0] > arr[1]) { small_first = arr[1]; small_second = arr[0]; } else { small_first = arr[0]; small_second = arr[1]; } //traverse all elements in the array for (int i = 2; i < arr.length; i++) { //compare smallest number with current number if(arr[i]<=small_first) { small_second = small_first; small_first = arr[i]; } else if(arr[i]<small_second){ small_second = arr[i]; } } //print smallest number from the array System.out.println("Second smallest element in the array: " + small_second); } }

Output:

Second smallest element in the array: 8

#### Python Program

**Prerequisites:**

- Python List (Python has a list that works similarly to the array from C/C++ and Java.)
- for-loop in Python
- if-else in Python

**Python Code:**

#initialize the Python list int_arr = [45, 56, 83, 4, 11, 28, 36] small_first = int_arr[0] small_second = int_arr[0] #initializ first and second smallest number if int_arr[0] > int_arr[1]: small_first = int_arr[1] small_second = int_arr[0] else: small_first = int_arr[0] small_second = int_arr[1] #loop over all the number in the list for num in int_arr[2:]: #compare smallest number with current number if num<=small_first: small_second = small_first small_first = num elif num<small_second: small_second = num print(f"Second smallest number in the Python list: {small_second}")

**Output:**

Second smallest number in the Python list: 11

#### Complexity

To find the second smallest number from the array, we are traversing the array only once. Each element in the array is visited once. So the time complexity of this algorithm is `O(n)`

. Here, `n`

is the size of the array.

We are using extra space to store the first and second smallest number but it is constant (irrespective of the size of the array.)

**What’s Next?**

Write a program to find the **second largest number in the array** and share it with me in the comment.