53. Maximum Subarray

Medium

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.

解題

經典 Greedy 題！

func maxSubArray(nums []int) int {
    max := nums[0]
    
    for i:=1; i<len(nums); i++ {
        if nums[i-1] + nums[i] > nums[i] {
            nums[i] = nums[i-1] + nums[i]
        } 
        
        if nums[i] > max {
            max = nums[i]
        }
    }
    
    return max
}