https://leetcode.cn/problems/maximum-length-of-subarray-with-positive-product/submissions/

class Solution {
public:
    int getMaxLen(vector<int>& nums) {
        int n =nums.size();
        vector<int> f(n+1, 0);
        auto g = f;
        // dp
        int ret = 0;
        for(int i=1; i<=n; ++i)
        {
            int x = f[i-1] + 1, y = g[i-1]==0 ? 0 : g[i-1] + 1;
            if(nums[i - 1] > 0)
            {
                f[i] = x;
                g[i] = y;
            }
            else if(nums[i - 1] < 0)
            {
                f[i] = y;
                g[i] = x;
            }

            ret = max(ret, f[i]);
        }
        return ret;
    }
};