leetcode 152. 乘积最大子数组

152. 乘积最大子数组

class Solution {
public:
    int maxProduct(vector<int>& nums) {
        if(nums.size() == 0) return 0;
        int imax = nums[0], imin = nums[0];
        int ans = nums[0];
        for(int ii = 1; ii < nums.size(); ii++) {
            if(nums[ii] < 0) swap(imax, imin);
            imin = min(nums[ii], imin * nums[ii]);
            imax = max(nums[ii], imax * nums[ii]);
            ans = max(ans, imax);
        }
        return ans;
    }
};

class Solution {
public:
    int calProduct(vector<int>& nums, int left, int right) {
        if(left >= right) return INT_MIN;
        int product = 1;
        while(left < right) product *= nums[left++];
        return product;
    }
    int maxProduct(vector<int>& nums) {
        int left = 0;
        int first_neg = -1, last_neg = -1, neg_cnt = 0;
        int ans = INT_MIN;
        nums.push_back(0);
        for(int ii = 0; ii < nums.size(); ii++) {
            if(nums[ii] == 0) {
                int temp = INT_MIN;
                if(ii - left == 1) temp = nums[left];
                else if((neg_cnt & 1) == 0) temp = calProduct(nums, left, ii);
                else temp = max(calProduct(nums, left, last_neg), calProduct(nums, first_neg+1, ii));
                ans = max(ans, temp);
                if(ii != nums.size()-1) ans = max(ans, 0);
                left = ii + 1;
                first_neg = -1, last_neg = -1;
                neg_cnt = 0;
            }
            else if(nums[ii] < 0) {
                if(first_neg == -1) first_neg = ii;
                last_neg = ii;
                neg_cnt++;
            }
        }
        return ans;
    }
};