构建乘积数组

class Solution {
public:
    vector<int> multiply(const vector<int>& nums) {
        int n=nums.size();
        if(n==0) return vector<int>();
        vector<int> q(n,1);
        for (int i = 1,t=nums[0]; i < n; i ++ )//t记录前i个数的乘积
        {
            q[i]=t;
            t*=nums[i];
        }
        for (int i = n-2,t=nums[n-1]; i >= 0; i -- )//t记录后i个数的乘积
        {
            q[i]*=t;
            t*=nums[i];
        }
        return q;
    }
};