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.

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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.

分析：考虑下标为i的元素，如果前面的元素之和小于0，那么对于增大在该元素的和是没有作用的。所以，将前面的和置为0. 运行时间14ms。

 1 class Solution {
 2 public:
 3     int maxSubArray(vector<int>& nums) {
 4         int sum = nums[0];
 5         int maxSum = nums[0];
 6         for(int i = 1; i < nums.size(); i++){
 7             if(sum < 0) sum = 0;
 8             sum += nums[i];
 9             maxSum = maxSum > sum ? maxSum : sum;
10         }
11         return maxSum;
12     }
13 };