leetcode53，二分法，为什么会超过时间限制？

Question

class Solution {
public:
    int maxSubArray(vector<int>& nums) {
        return divide(nums, 0, nums.size()-1);
    }

private:
    int divide(vector<int> &nums,int l,int r){
        if(l >= r) return nums[l];
        int mid = (l + r) / 2;
        int lmax = divide(nums,l,mid - 1);
        int rmax = divide(nums,mid + 1,r);
        int mid_l = nums[mid];
        //计算左边最大的串
        for(int i = mid - 1 ,sum = nums[mid];i >= l ;--i){
            sum += nums[i];
            mid_l = max(sum , mid_l);
        }
        //与右边的合并
        int mid_r = mid_l;
        for(int i = mid +1 ,sum = mid_r;i <= r;++r){
            sum += nums[i];
            mid_r = max(sum,mid_r);
        }
        return max(lmax,max(rmax,mid_r));
    }

};

基本上就是抄写的这里的二分法，但是却会超过时间限制，请问为什么呢？

Answer 1

最后一个for循环写错了，是++i不是++r

Answer 2

楼主可以考虑一下O(N)的算法