题解 | #子数组最大乘积#

class Solution {
public:
    double maxProduct(vector<double> arr) {
        int n = arr.size();
        if(arr.size() < 1)
            return 0.0;
        // 初始化，因为乘积需要考虑负数情况,所以要设置一个minN来保存最小值
        double maxN = arr[0];
        double minN = arr[0];
        double res = arr[0];;
        for(int i = 1; i < n; i++) {
            // 保存上一步的最大值和最小值
            double mx = maxN, mi = minN;
            maxN = max(mx * arr[i], max(arr[i], mi * arr[i]));
            minN = min(mi * arr[i], min(arr[i], mx * arr[i]));
            res = max(res, maxN);
        }
        return res;
    }
};