MaximumProductSubarray.java

package dynamic_programming;

/**
 * Created by gouthamvidyapradhan on 02/04/2017.
 Find the contiguous subarray within an array (containing at least one number) which has the largest product.

 For example, given the array [2,3,-2,4],
 the contiguous subarray [2,3] has the largest product = 6.
 */
public class MaximumProductSubarray
{
    /**
     * Main method
     * @param args
     * @throws Exception
     */
    public static void main(String[] args) throws Exception
    {
        int[] A = {2,3,-2,4};
        System.out.println(new MaximumProductSubarray().maxProduct(A));
    }

    public int maxProduct(int[] nums)
    {
        if(nums.length == 1) return nums[0];
        int min = nums[0];
        int max = nums[0];
        int result = max;
        for(int i = 1; i < nums.length; i ++)
        {
            int prevMin = min, prevMax = max;
            min = Math.min(nums[i], Math.min(nums[i] * prevMin, nums[i] * prevMax));
            max = Math.max(nums[i], Math.max(nums[i] * prevMin, nums[i] * prevMax));
            result = Math.max(result, max);
        }
        return result;
    }
}