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.
这道题需要用动态规划方法解决（自底向上），首先动态规划有两个特点，一个是最优子结构，另一个是重叠子问题。我们先求出子问题的最小乘积（可能会是负数）和最大乘积，然后与当前的数组值相乘和当前的值进行比较（maxhere和minhere），同样保存最大值和最小值。代码如下：
public class Solution {
public int maxProduct(int[] nums) {
int maxherepre = nums[0];
int minherepre = nums[0];
int maxsofar = nums[0];
int maxhere=nums[0],minhere=nums[0];
for(int i=1;i<nums.length;i++){
maxhere = Math.max(nums[i],Math.max(maxherepre*nums[i],minherepre*nums[i]));
minhere = Math.min(nums[i],Math.min(maxherepre*nums[i],minherepre*nums[i]));
maxsofar = Math.max(maxsofar,maxhere);
maxherepre = maxhere;
minherepre = minhere;
}
return maxsofar;
}
}