Data Structure
Networking
RDBMS
Operating System
Java
MS Excel
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
Physics
Chemistry
Biology
Mathematics
English
Economics
Psychology
Social Studies
Fashion Studies
Legal Studies
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
Maximum subarray sum in an array created after repeated concatenation in C++ Program
In this problem, we are given an array arr[] of size n and an integer k. Our task is to create a program to find the maximum subarray sum in an array created after repeated concatenation.
Problem Description − We will find the maximum sum of the subarray is taken from the array which is created after repeating arr, k times.
Example
Let’s take an example to understand the problem.
Input
arr[] = {−9, −5, 14, 6} k = 2Output
26
Explanation
New array after repeating : {−9, −5, 14, 6, −9, −5, 14, 6}
Subarray with maximum sum = {14, 6, −9, −5, 14, 6}
Sum = 26Solution Approach
A simple solution is to create a new array that will be formed after concatenating arr[], k time, and then find the subarray with maximum sum. For this, the best method would be using Kadane's Algorithm.
Example
Program to illustrate the working of our solution,
#include <iostream>
using namespace std;
int calcMaxSubArraySum(int arr[], int n, int k){
int newArr[2*n];
for(int i = 0; i < k*n; i++)
newArr[i] = arr[i%n];
int maxSum = −1000, sum = 0;
for (int i = 0; i < k*n; i++) {
sum = sum + newArr[i];
if (maxSum < sum)
maxSum = sum;
if (sum < 0)
sum = 0;
}
return maxSum;
}
int main(){
int arr[] = { −9, −5, 14, 6 };
int k = 2;
int n = sizeof(arr) / sizeof(arr[0]);
cout<<"The maximum subarray sum in an array created after repeated concatenation is "<<calcMaxSubArraySum(arr, n, k);
return 0;
}Output
The maximum subarray sum in an array created after repeated concatenation is 26
This approach is good but a more efficient approach to solving the problem is possible using modular arithmetic.
Modular Arithmetic is when we use the modulo operator to get the remainder of the equation.
To solve the problem, we will use modular arithmetic instead of creating the array by repeated concatenation. Rest solution remains the same.
Example
Program to illustrate the working our solution,
#include <iostream>
using namespace std;
int calcMaxSubArraySum(int arr[], int n, int k){
int maxSum = −1000, sum = 0;
for (int i = 0; i < k*n; i++) {
sum = sum + arr[i%n];
if (maxSum < sum)
maxSum = sum;
if (sum < 0)
sum = 0;
}
return maxSum;
}
int main(){
int arr[] = { −9, −5, 14, 6 };
int k = 2;
int n = sizeof(arr) / sizeof(arr[0]);
cout<<"The maximum subarray sum in an array created after
repeated concatenation is "<<calcMaxSubArraySum(arr, n, k);
return 0;
}Output
The maximum subarray sum in an array created after repeated concatenation is 26
101 Views
