Leetcode Maximum Product Subarray

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.

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解题思路：

This is similar to maximum subarray. Instead of sum, the sign of number affect the product value.

When iterating the array, each element has two possibilities: positive number or negative number. We need to track a minimum value, so that when a negative number is given, it can also find the maximum value. We define two local variables, one tracks the maximum and the other tracks the minimum.

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Java code:

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

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Reference:

1. http://www.programcreek.com/2014/03/leetcode-maximum-product-subarray-java/