Find the smallest contiguous sum pair in an Array

Given an array arr[] containing N distinct integers, the task is to find a contiguous pair such that the sum of both elements in the pair is minimum.

Examples:

Input: arr[] = {1, 2, 3, 4} 
Output: (1, 2) 
Explanation:
Here, contiguous pairs with their sum are (1, 2) = 3, (2, 3) = 5, (3, 4) = 7 and the minimum is 3.
Input: arr[] = {4, 9, -3, 2, 0} 
Output: (-3, 2) 
Explanation:
Here, contiguous pairs with their sum are (4, 9) = 13, (9, -3) = 6, (-3, 2) = -1, (2, 0) = 2

Approach:
To solve the problem mentioned above, we have to consider all the contiguous pairs and find their sum. The pair having the smallest(minimum) sum is the required answer.
Below is the implementation of the above approach:

C++

//C++ program to find the smallest
// sum contiguous pair
#include<bits/stdc++.h>
using namespace std;

// Function to find the smallest sum
// contiguous pair
vector<int> smallestSumpair(int arr[], int n)
{

    // Contiguous pair
    vector<int>pair;

    // Initialize minimum sum
    // with maximum value
    int min_sum = INT_MAX;

    for(int i = 1; i < n; i++)
    {

        // Checking for minimum value
        if( min_sum > (arr[i] + arr[i - 1]))
        {
            min_sum = arr[i] + arr[i - 1];
            if (pair.empty())
            {

                // Add to pair
                pair.push_back(arr[i - 1]);
                pair.push_back(arr[i]);
            }
            else
            {

                // Updating pair
                pair[0] = arr[i - 1];
                pair[1] = arr[i];
            }
        }
    }
    return pair;
}

// Driver code
int main()
{
   int arr[] = {4, 9, -3, 2, 0};
   int n = sizeof(arr) / sizeof(arr[0]);

   vector<int>pair = smallestSumpair(arr, n);
   cout << pair[0] << " " << pair[1];
}

// This code is contributed by chitranayal

Java

// Java program to find the smallest
// sum contiguous pair
import java.util.*;

class GFG{

// Function to find the smallest sum
// contiguous pair
public static Vector<Integer> smallestSumpair(int[] arr,
                                              int n)
{

    // Stores the contiguous pair
    Vector<Integer> pair = new Vector<Integer>();

    // Initialize minimum sum
    int min_sum = Integer.MAX_VALUE, i;

    for(i = 1; i < n; i++)
    {

        // Checking for minimum value
        if (min_sum > (arr[i] + arr[i - 1]))
        {
            min_sum = arr[i] + arr[i - 1];

            if (pair.isEmpty())
            {

                // Add to pair
                pair.add(arr[i - 1]);
                pair.add(arr[i]);
            }
            else
            {

                // Updating pair
                pair.set(0, arr[i - 1]);
                pair.set(1, arr[i]);
            }
        }
    }
    return pair;
}

// Driver Code
public static void main(String[] args)
{
    int arr[] = { 4, 9, -3, 2, 0 };
    int N = arr.length;

    Vector<Integer> pair = new Vector<Integer>();
    pair = smallestSumpair(arr, N);

    System.out.println(pair.get(0) + " " +
                       pair.get(1));
}
}

// This code is contributed by divyeshrabadiya07

Python3

# Python3 program to find the smallest
# sum contiguous pair

# importing sys
import sys

# Function to find the smallest sum
# contiguous pair


def smallestSumpair(arr, n):

    # Contiguous pair
    pair = []

    #  Initialize minimum sum
    # with maximum value
    min_sum = sys.maxsize

    for i in range(1, n):

        # checking for minimum value
        if min_sum > (arr[i] + arr[i-1]):
            min_sum = arr[i] + arr[i-1]

            if pair == []:

                # Add to pair
                pair.append(arr[i-1])
                pair.append(arr[i])
            else:

                # Updating pair
                pair[0] = arr[i-1]
                pair[1] = arr[i]

    return pair


# Driver code
arr = [4, 9, -3, 2, 0]
n = len(arr)
pair = smallestSumpair(arr, n)
print(pair[0], pair[1])

C#

// C# program to find the smallest
// sum contiguous pair
using System;
using System.Collections;
using System.Collections.Generic;

class GFG{

// Function to find the smallest sum
// contiguous pair
public static ArrayList smallestSumpair(int[] arr,
                                        int n)
{

    // Stores the contiguous pair
    ArrayList pair = new ArrayList();

    // Initialize minimum sum
    int min_sum = int.MaxValue, i;

    for(i = 1; i < n; i++)
    {

        // Checking for minimum value
        if (min_sum > (arr[i] + arr[i - 1]))
        {
            min_sum = arr[i] + arr[i - 1];

            if (pair.Count == 0)
            {

                // Add to pair
                pair.Add(arr[i - 1]);
                pair.Add(arr[i]);
            }
            else
            {

                // Updating pair
                pair[0] = arr[i - 1];
                pair[1] = arr[i];
            }
        }
    }
    return pair;
}

// Driver code
public static void Main(string[] args)
{
    int []arr = { 4, 9, -3, 2, 0 };
    int N = arr.Length;

    ArrayList pair = new ArrayList();
    pair = smallestSumpair(arr, N);

    Console.Write(pair[0] + " " + pair[1]);
}
}

// This code is contributed by rutvik_56

Javascript

<script>
// Javascript program to find the smallest
// sum contiguous pair

// Function to find the smallest sum
// contiguous pair
function smallestSumpair(arr,n)
{
    // Stores the contiguous pair
    let pair = [];

    // Initialize minimum sum
    let min_sum = Number.MAX_VALUE, i;

    for(i = 1; i < n; i++)
    {

        // Checking for minimum value
        if (min_sum > (arr[i] + arr[i - 1]))
        {
            min_sum = arr[i] + arr[i - 1];

            if (pair.length==0)
            {

                // Add to pair
                pair.push(arr[i - 1]);
                pair.push(arr[i]);
            }
            else
            {

                // Updating pair
                pair[0] = arr[i - 1];
                pair[1] = arr[i];
            }
        }
    }
    return pair;
}

// Driver Code
let arr=[4, 9, -3, 2, 0 ];
let  N = arr.length;
let pair = smallestSumpair(arr, N);

document.write(pair[0] + " " +
                   pair[1]);




// This code is contributed by rag2127
</script>

Output

-3 2

Time Complexity: O(n)