题解 | #构建乘积数组#

class Solution {
public:
    vector<int> multiply(const vector<int>& A) {
      if (A.empty() || A.size() == 1) {
        return std::vector<int>();
      }
      
      std::vector<int> res(A.size(), 1);
      
      //  得出下三角
      for (int i = 1; i < A.size(); ++i) {
        res[i] = res[i - 1] * A[i - 1];
      }
      
      int tmp = 1;
      //  上三角
      for (int i = A.size() - 1; i >= 0; --i) {
        res[i] *= tmp;
        tmp *= A[i];
      }
      
      return res;
    }
};