152. Maximum Product Subarray

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.

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分析：如果遇到负数，乘以这个数，原来的最大可能变成最小，最小可能变成最大，因此，要记录之前的最大和最小。

 int maxProduct(vector<int>& nums) {        int n=nums.size();        if(n<0)return 0;        int r=nums[0];        int maxn,minn;        minn=maxn=nums[0];        for(int i=1;i<n;i++)        {            if(nums[i]<0)            swap(minn,maxn);            maxn=max(nums[i],maxn*nums[i]);            minn=min(nums[i],minn*nums[i]);            r=max(r,maxn);        }        return r;    }