Lintcode - Maximum Subarray II

Given an array of integers, find two non-overlapping subarrays which have the largest sum.

The number in each subarray should be contiguous.

Return the largest sum.

Note

The subarray should contain at least one number

Example

For given [1, 3, -1, 2, -1, 2], the two subarrays are [1, 3] and [2, -1, 2] or [1, 3, -1, 2] and [2], they both have the largest sum 7.

思路和股票买卖III一样：

分层两段，左边和右边分别计算max subarray，然后两边加起来最大的就是结果。

这道题目里没有明确说一定要两段（比如一段可不可以，比如左边没有值，右边有一段），但是实际结果是一段是不可以的。。。

    public int maxTwoSubArrays(ArrayList<Integer> nums) {        int[] left = new int[nums.size()];        int localMax = 0;        int globalMax = Integer.MIN_VALUE;        for (int i = 0; i < nums.size(); i++) {            localMax = Math.max(nums.get(i), localMax + nums.get(i));            globalMax = Math.max(localMax, globalMax);            left[i] = globalMax;        }                localMax = 0;        globalMax = Integer.MIN_VALUE;        int result = Integer.MIN_VALUE;        for (int i = nums.size()-1; i >= 0; i--) {            if (i < nums.size()-1) {                result = Math.max(result, left[i] + globalMax);            }            localMax = Math.max(nums.get(i), localMax + nums.get(i));            globalMax = Math.max(localMax, globalMax);        }        return result;    }