Maximum Subarray

题目：
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.

解答：

//贪心算法，时间复杂度O(n)
class Solution {
public:
    int maxSubArray(vector<int>& nums) {
        int ans = -100000000;
        int sum = 0;
        int temp = nums[0] ;
        int n = nums.size();
        for(int i=0; i<n; i++)
        {
            if(temp < nums[i])
                temp = nums[i];  //最大值

            sum = sum + nums[i];
            if(sum > ans)
                ans =sum;
            if(sum < 0)   //sum为0，前面的这个数必然为负数，舍弃
                sum =0;
        }

        if(temp <= 0)   //如和为负数，则直接答案为最大值
            ans = temp;
        return ans;
    }
};