在 C++ 中移动语义二维向量

Question

我对二维向量（或向量的向量）中的 C++ 移动语义有疑问。它来自动态规划的问题。为了简单起见，我只是以简化版为例。

//suppose I need to maintain a 2D vector of int with size 5 for the result. 
vector<vector<int>> result = vector<vector<int>>(5);

for(int i = 0; i < 10; i++){
  vector<vector<int>> tmp = vector<vector<int>>(5);
  
  //Make some updates on tmp with the help of result 2D vector
  
  /*
    Do something
  */

  //At the end of this iteration, I would like to assign the result by tmp to prepare for next iteration.

  // 1) The first choice is to make a copy assignment, but it might introduce some unnecessary copy
  // result = tmp;

  // or

  // 2) The second choice is to use move semantics, but I not sure if it is correct on a 2D vector. 
  // I am sure it should be OK if both tmp the result are simply vector (1D).
  // result = move(tmp);

}

那么，简单地使用 `result = move(tmp);' 可以吗？二维向量的移动语义？

Answer 1

是的，因为结果不是“二维”向量，它只是向量的一维向量。

在 C++ 中移动语义二维向量

move semantics 2d vector in C++

c++

vector

move-semantics