The sum of Elements Between k1th and k2th smallest elements

We need to find the sum of the elements between the given two indexes of the given vector.

Where the user provides the two indexes and the input vector.

Let us understand through an example:

If the vector is [ 1 4 2 6 8 11 10] and k1, k2 are 2,5.

Here, we must find the sum of numbers between the k1 and k2 indexes.

But first, we need to sort the given vector and sum the values from the k1 to the k2 index.

So, after sorting, the vector becomes as follows:

[1 2 4 6 8 10 11].

If we consider the indexes form 0, the sum of values from index 2 to index 5 is 4+6+8+10 = 28.

Now we need to implement a code to find the sum of values between the k1 and k2 index, including the k1 and k2 indexes:

CODE:

#include <bits/stdc++.h>
using namespace std;
int main() {
    int n;
cout<< " Enter the size of vector: ";
cin>> n;
    vector< int >vec;

    // taking input vector

for(int i = 0; i< n; i++) {
cout<< " Enter " << i+1 << " value: ";
        int x;
cin>> x;
vec.push_back(x);
    }

    //Now, we need to sort the given vector so that 
    //We can easily access the smaller elements from the vector.

    sort(vec.begin(), vec.end());

    // taking input for k1 nad k2 indexes

    int k1, k2;
cout<< " Enter k1 and k2 values: ";
cin>> k1 >> k2;
if(k2 < k1) {
swap(k1, k2);
    }
if(k1>=n || k2>=n){
        if(k1>=n && k2>=n){
cout<<" k1 and k2 values cannot be greater than or equal to n";
        }
        if(k1>=n ){
cout<<" k1 value cannot be greater than or equal to n";
        }
else{
cout<<" k2 value cannot be greater than or equal to n";
        }
exit(0);
    }
    int sum = 0;
    // printing the elements that make the sum
    //Also calculating the sum
cout<< " Elements are: ";
for(int i = k1; i<= k2; i++) {
        sum += vec[i];
cout<<vec[i] << " ";
    }
cout<< " sum is: " << sum;
    return 0;
}

Output:

The sum of Elements Between k1th and k2th smallest elements

Explanation:

First, we have included the required libraries for the execution of the code.

for(int i = 0; i< n; i++) {
cout<< " Enter " << i+1 << " value: ";
        int x;
cin>> x;
vec.push_back(x);
    }

This part of the code will take the vector elements as input and get stored in the vector named vec.

Next, we need to sort the vector to easily traverse the smallest elements from

index k1 to index k2.
sort(vec.begin(), vec.end());

The above line of code will sort the given input vector, where sort is an inbuilt function that takes parameters as the address of the vector beginning and ending.

Next, we need to prompt the user to enter the k1 and k2 indexes to find the sum of elements between the k1 and k2 indexes.

int k1, k2;
cout<< " Enter k1 and k2 values: ";
cin>> k1 >> k2;
if(k2 < k1) {
swap(k1, k2);
    }

This part of the code will handle taking input for ka and k2 values, and we also swap k1 k2 if k2<k1 because if k2<k1, we cannot iterate through the loop.

So, we swapped both elements.

Next, we need to calculate the sum from index k1 to index k2, and we will also print the values that make that sum.

for(int i = k1; i<= k2; i++) {
        sum += vec[i];
cout<<vec[i] << " ";
    }

The above loop calculates the sum of elements between the k1 and k2 indexes, including k1 and k2 indexes.

It will also print the elements that are making the sum.

And finally, we will print the sum of values from index k1 to index k2.

We will also handle cases where the user gives a k1 or k2 value greater than or equal to n. In this case, we cannot calculate the sum because we will get an error called vector index out of bound, i.e., we are trying to access the elements that are not in the vector.

The below code is responsible for handling those cases.

if(k1>=n || k2>=n){
        if(k1>=n && k2>=n){
cout<<" k1 and k2 values cannot be greater than n";
        }
        if(k1>=n ){
cout<<" k1 value cannot be greater than or equal to n";
        }
        else
cout<<" k2 value cannot be greater than or equal to n";
        }
}

Output for handling this case is: