53. Maximum Subarray

题目：

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.

算法

只需要从头到尾遍历一次，
如果当前总和<0, 那么加后面一个数字肯定不如从后面一个数字重新开始，
如果如果当前总和>0，就可以加后面的一个数字，
最后和当前最大值进行比较，取最大

复杂度：O(n)

代码

int maxSubArray(int* nums, int size)
{
    int sum = 0;
    int max = INT_MIN;
    for(int i = 0; i < size; i++)
    {
        if(sum >= 0)
            sum += nums[i];
        else
            sum = nums[i];
        if(sum > max)
            max = sum;
    }
    return max;
}