Java Program for Largest Sum Contiguous Subarray

Write an efficient program to find the sum of contiguous subarray within a one-dimensional array of numbers which has the largest sum.

kadane-algorithm

Recommended: Please solve it on “PRACTICE ” first, before moving on to the solution.

Java

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import java.io.*;
// Java program to print largest contiguous array sum
import java.util.*;
  
class Kadane {
    public static void main(String[] args)
    {
        int[] a = { -2, -3, 4, -1, -2, 1, 5, -3 };
        System.out.println("Maximum contiguous sum is " + maxSubArraySum(a));
    }
  
    static int maxSubArraySum(int a[])
    {
        int size = a.length;
        int max_so_far = Integer.MIN_VALUE, max_ending_here = 0;
  
        for (int i = 0; i < size; i++) {
            max_ending_here = max_ending_here + a[i];
            if (max_so_far < max_ending_here)
                max_so_far = max_ending_here;
            if (max_ending_here < 0)
                max_ending_here = 0;
        }
        return max_so_far;
    }
}

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Output:

Maximum contiguous sum is 7

Above program can be optimized further, if we compare max_so_far with max_ending_here only if max_ending_here is greater than 0.

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static int maxSubArraySum(int a[], int size)
{
  
    int max_so_far = 0, max_ending_here = 0;
  
    for (int i = 0; i < size; i++) {
        max_ending_here = max_ending_here + a[i];
        if (max_ending_here < 0)
            max_ending_here = 0;
  
        /* Do not compare for all
           elements. Compare only 
           when max_ending_here > 0 */
        else if (max_so_far < max_ending_here)
            max_so_far = max_ending_here;
    }
    return max_so_far;
}
  
// This code is contributed by ANKITRAI1

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Please refer complete article on Largest Sum Contiguous Subarray for more details!




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