LeetCode Online Judge 题目C# 练习 - Maximum Subarray

Find the contiguous subarray within an array (containing at least one number) which has the largest sum.
For example, given the array [−2,1,−3,4,−1,2,1,−5,4],
the contiguous subarray [4,−1,2,1] has the largest sum = 6.
More practice:
If you have figured out the O(n) solution, try coding another solution using the divide and conquer approach, which is more subtle.

 1         public static int MaximumSubarray(int[] A)

 2         {

 3             int n = A.Length;

 4             int max = A[0], max_neg = A[0], sum = 0;

 5             bool flag = false; // for all the elements are negative integers

 6             for (int i = 0; i < n; i++)

 7             {

 8                 //if found one is not negative, toggle flag. And keep tracking the max negative number

 9                 if (A[i] >= 0)

10                     flag = true;

11                 else if (A[i] > max_neg)

12                     max_neg = A[i];

13 

14                 sum += A[i];

15                 if (sum < 0)

16                     sum = 0;

17                 else if (sum > max)

18                     max = sum;

19             }

20 

21             return flag ? max : max_neg;

22         }

代码分析：

　　O(n)的解法， 要注意所有element都是negative的case。