LeetCode Maximum Subarray

Find the contiguous subarray within an array (containing at least one number) which has the largest sum.

For example, given the array [-2,1,-3,4,-1,2,1,-5,4],
the contiguous subarray [4,-1,2,1] has the largest sum = 6.

思路一：暴力搜索，最笨的方法

代码如下：

class Solution {public:    int maxSubArray(vector<int>& nums) {        int size = nums.size();        int max = 0x80000000,sum=0;        for(int i=0;i<size;i++)        {            sum = 0;            for(int j=i;j<size;j++)            {                sum += nums[j];                if(sum > max)                    max = sum;            }        }        return max;    }};

已哭晕在厕所，想想怎么优化

思路二：寻找特性，进行减枝操作。当sum小于0时，其加上后面的数只会使得sum更小，所以此时sum与max进行对比，然后就sum置为0，从下一个位置开始计算

代码如下：

class Solution {public:    int maxSubArray(vector<int>& nums) {        int size = nums.size();        int max = 0x80000000,sum=0;        for(int i=0;i<size;i++)        {            sum += nums[i];            if(sum > max)                max = sum;            if(sum < 0)                sum = 0;        }        return max;    }};