152. Maximum Product Subarray

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

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

题意：找出数组中最大的连续片段乘积。

思路：max(n) = max{ max(n-1), product(...n) }, product是连续乘积到n的最大正值(包含a[n]的连续最大乘积)。所以需记录连续乘积到n-1的最大的正负值。

class Solution {public:int maxProduct(vector<int>& nums) {if (nums.size() < 1)return 0;int maxNum = (numeric_limits<int>::min)();int positive = 1;int negative = 1;for (int i = 0; i < nums.size(); i++){if (nums[i] >= 0){positive *= nums[i];negative *= nums[i];}else{int tmp = positive;positive = negative * nums[i];negative = tmp * nums[i];}if (positive > maxNum)maxNum = positive;if (positive <= 0)positive = 1;if (negative >= 0)negative = 1;}return maxNum;}};