LeetCode-in-All
53. Maximum Subarray
Easy
Given an integer array nums, find the contiguous subarray (containing at least one number) which has the largest sum and return its sum.
A subarray is a contiguous part of an array.
Example 1:
Input: nums = [-2,1,-3,4,-1,2,1,-5,4]
Output: 6
Explanation: [4,-1,2,1] has the largest sum = 6.
Example 2:
Input: nums = [1]
Output: 1
Example 3:
Input: nums = [5,4,-1,7,8]
Output: 23
Constraints:
1 <= nums.length <= 105-104 <= nums[i] <= 104
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.
Solution
# @param {Integer[]} nums
# @return {Integer}
def max_sub_array(nums)
sum_so_far = 0
max_sum = -Float::INFINITY
end_ptr = 0
while end_ptr < nums.length
sum_so_far += nums[end_ptr]
max_sum = [max_sum, sum_so_far].max
sum_so_far = 0 if sum_so_far < 0
end_ptr += 1
end
max_sum
end