> For the complete documentation index, see [llms.txt](https://lex47.gitbook.io/leetcode/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://lex47.gitbook.io/leetcode/leet-solution-ruby/53.md).

# 53. Maximum Subarray

Given an integer array `nums`, find the contiguous subarray (containing at least one number) which has the largest sum and return its sum.

**Example:**

```
Input: [-2,1,-3,4,-1,2,1,-5,4],
Output: 6
Explanation: [4,-1,2,1] has the largest sum = 6.
```

**Follow up:**

If you have figured out the O(*n*) solution, try coding another solution using the divide and conquer approach, which is more subtle.

```
# @param {Integer[]} nums
# @return {Integer}
def max_sub_array(nums)
  return 0 if nums.nil?
  return nums[0] if nums.length == 1
  
  cur = nums[0]
  sum = nums[0]
  for i in 1...nums.length do
    cur = cur > 0 ? cur + nums[i] : nums[i]
    sum = cur if cur >= sum
  end
  sum
  
end
```