LeetCode 53 ，分治解

class Solution {
    public int maxSubArray(int[] nums) {
        if(nums == null || nums.length == 0) return 0;
        return maxSubArray(nums,0,nums.length-1);
    }
    private int maxSubArray(int[] nums,int L,int R) {
        if(L == R) return nums[L];
        int mid = L+(R-L>>1);
        int left = maxSubArray(nums,L,mid);
        int right = maxSubArray(nums,mid+1,R);
        int middle = maxCsArray(nums,L,mid,R);
        if(left>=right&&left>=middle) return left;
        else if(right>=left&&right>=middle) return right;
        else return middle;
    }
    private int maxCsArray(int[] nums,int L,int mid,int R) {
        int leftSum = Integer.MIN_VALUE;
        int sum = 0;
        for(int i = mid;i>=L;i--) {
            sum+=nums[i];
            if(sum > leftSum) leftSum = sum;
        }
        int rightSum = Integer.MIN_VALUE;
        sum = 0;
        for(int i = mid+1 ;i<=R;i++) {
            sum+=nums[i];
            if(sum>rightSum) rightSum = sum;
        }
        return leftSum+rightSum;
    }
}

借鉴部分，需要好好品味其中分治的精髓，虽然可以用其他较好方法