Given an array arr[] of size N which contains at least one composite number. The task is to find out the sum of all the composite numbers in the array which are at odd indices (where indexing is 1 based).
Examples:
Input: arr = [13, 5, 8, 16, 25]
Output: 33
Explanation:
The number in the odd indices are 13, 8, 25 since we follow 1 based indexing.
Out of all these 3 numbers, the composite numbers are 8 and 25, which sums to 33.Input: arr = [9, 7, 14, 10, 34]
Output: 57
Explanation:
The number in the odd indices are 9, 14, 34 since we follow 1 based indexing.
All three numbers are composite numbers, which sums to 57.
Approach:
To solve the problem mentioned above the main idea is to check for the composite numbers that is, if an integer has more than 2 factors then it’s a composite number otherwise it is not. Then we will iterate and check for the composite numbers in odd indices of the array. If it is a composite number then we will add it to the sum variable otherwise skip it until the end of the array reaches.
Below is the implementation of the above approach:
// C++ implementation to find the sum of all the// composite numbers from odd indices of the given array#include<bits/stdc++.h>using namespace std;
// Function to check for composite numbersint composite(int n){
int flag = 0;
int c = 0;
// Check if the factors are greater than 2
for (int j = 1; j <= n; j++){
if (n % j == 0){
c += 1;
}
}
// Check if the number is composite or not
if (c >= 3)
flag = 1;
return flag;
} // Function to print the sum of all // composite numbers in the arrayvoid odd_indices(int arr[],int n){
int sum = 0;
// Iterate for odd indices in the arrayfor (int k = 0; k < n; k += 2){
int check = composite(arr[k]);
// Check if the number is composite
// then add it to sum
if (check == 1)
sum += arr[k];
} // return the sum
cout << sum << endl;
}// Driver code int main(){
int arr[] = {13, 5, 8, 16, 25};
int n = sizeof(arr)/sizeof(arr[0]);
odd_indices(arr,n);
}// This code is contributed by Surendra_Gangwar |
// Java implementation to find the sum of all the// composite numbers from odd indices of the given arrayclass GFG{
// Function to check for composite numbersstatic int composite(int n){
int flag = 0;
int c = 0;
// Check if the factors are greater than 2
for (int j = 1; j <= n; j++){
if (n % j == 0){
c += 1;
}
}
// Check if the number is composite or not
if (c >= 3)
flag = 1;
return flag;
} // Function to print the sum of all // composite numbers in the arraystatic void odd_indices(int arr[],int n){
int sum = 0;
// Iterate for odd indices in the arrayfor (int k = 0; k < n; k += 2){
int check = composite(arr[k]);
// Check if the number is composite
// then add it to sum
if (check == 1)
sum += arr[k];
} // return the sum
System.out.print(sum +"\n");
}// Driver code public static void main(String[] args){
int arr[] = {13, 5, 8, 16, 25};
int n = arr.length;
odd_indices(arr,n);
}}// This code contributed by sapnasingh4991 |
# Python3 implementation to find the sum of all the# composite numbers from odd indices of the given array# Function to print the sum of all # composite numbers in the arraydef odd_indices(arr):
sum = 0
# Iterate for odd indices in the array
for k in range (0, len(arr), 2):
check = composite (arr[k])
# Check if the number is composite
# then add it to sum
sum += arr[k] if check == 1 else 0
# return the sum
print (sum)
# Function to check for composite numbersdef composite(n):
flag = 0
c = 0
# Check if the factors are greater than 2
for j in range (1, n + 1):
if (n % j == 0):
c += 1
# Check if the number is composite or not
if (c >= 3):
flag = 1
return flag
# Driver code if __name__ == "__main__":
arr = [13, 5, 8, 16, 25]
odd_indices(arr)
|
// C# implementation to find the sum // of all the composite numbers from // odd indices of the given arrayusing System;
class GFG{
// Function to check for composite numbersstatic int composite(int n)
{ int flag = 0;
int c = 0;
// Check if the factors are greater than 2
for(int j = 1; j <= n; j++)
{
if (n % j == 0)
{
c += 1;
}
}
// Check if the number is composite or not
if (c >= 3)
flag = 1;
return flag;
} // Function to print the sum of all // composite numbers in the arraystatic void odd_indices(int []arr,int n)
{ int sum = 0;
// Iterate for odd indices in the array
for(int k = 0; k < n; k += 2)
{
int check = composite(arr[k]);
// Check if the number is composite
// then add it to sum
if (check == 1)
sum += arr[k];
}
// return the sum
Console.Write(sum + "\n");
}// Driver code public static void Main(String[] args)
{ int []arr = { 13, 5, 8, 16, 25 };
int n = arr.Length;
odd_indices(arr, n);
}}// This code is contributed by Rohit_ranjan |
<script>// Javascript implementation to find the sum of all the// composite numbers from odd indices of the given array// Function to check for composite numbersfunction composite(n){
let flag = 0;
let c = 0;
// Check if the factors are greater than 2
for (let j = 1; j <= n; j++){
if (n % j == 0){
c += 1;
}
}
// Check if the number is composite or not
if (c >= 3)
flag = 1;
return flag;
} // Function to print the sum of all // composite numbers in the arrayfunction odd_indices(arr, n){
let sum = 0; // Iterate for odd indices in the arrayfor (let k = 0; k < n; k += 2){
let check = composite(arr[k]);
// Check if the number is composite
// then add it to sum
if (check == 1)
sum += arr[k];
} // return the sum
document.write(sum + "<br>");
}// Driver code let arr = [13, 5, 8, 16, 25];
let n = arr.length
odd_indices(arr,n);
// This code is contributed by gfgking</script> |
33
Time Complexity: O(n * m), where n is the length of the given array and m is the maximum element in the array.
Auxiliary Space: O(1), no extra space is required, so it is a constant.