Q238 除自身以外数组的乘积

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class PrefixSuffixProduct
{public:
    vector<int> prefix;
    vector<int> suffix;
    PrefixSuffixProduct(vector<int>& nums)
    {
        int sz = nums.size();
        prefix.resize(sz+1,1);
        suffix.resize(sz+1,1);
        for(int i=1;i<=sz;i++)
        {
            prefix[i] = prefix[i-1] * nums[i-1];
        }
        for(int i=sz-1;i>=0;i--)
        {
            suffix[i] = suffix[i+1] * nums[i];
        }
    }
    int plus_matrix(int x1)
    {
        return prefix[x1] * suffix[x1+1];
    }
};

class Solution {
public:
    vector<int> productExceptSelf(vector<int>& nums) {
        vector<int> res;
        PrefixSuffixProduct am(nums);
        int sz = nums.size();
        res.resize(sz,1);
        for(int i = 0;i<sz;i++)
        {
           res[i] = am.plus_matrix(i);
        }
        return res;
    }
};