53. Maximum Subarray

這題我跪了!!!

題目原文

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.

解題思路

1. 偷偷搜尋一下Kadane's Algorithm.

程式解答

Kadane's Algorithm O(n)

class Solution 
{
public:
    int maxSubArray(vector<int>& nums) 
    {
        int max, sum;
        
        max = sum = nums[0];
        
        for (int i = 1; i < nums.size(); i++)
        {
            sum = std::max(nums[i], sum + nums[i]);
            max = std::max(max, sum);
        }
        return max;
    }
};