动态分配向量(或向量的向量)

allocating vectors (or vectors of vectors) dynamically(动态分配向量(或向量的向量))

问题描述

我需要动态分配大小在运行时给定的一维和二维数组.

I need to dynamically allocate 1-D and 2-D arrays whose sizes are given at run-time.

我设法发现"了 std::vector 并且我认为它符合我的目的，但我想问一下我写的内容是否正确和/或可以改进.

I managed to "discover" std::vector and I think it fits my purposes, but I would like to ask whether what I've written is correct and/or can be improved.

这就是我正在做的:

#include <vector>

typedef std::vector< std::vector<double> > matrix;

//... various code and other stuff

std::vector<double> *name = new std::vector<double> (size);
matrix *name2 = new matrix(sizeX, std::vector<double>(sizeY));

推荐答案

如您所见，在运行时给定维度时需要动态分配数组.

Dynamically allocating arrays is required when your dimensions are given at runtime, as you've discovered.

然而，std::vector 已经是这个过程的wrapper，所以动态分配向量就像一个双重肯定.这是多余的.

However, std::vector is already a wrapper around this process, so dynamically allocating vectors is like a double positive. It's redundant.

直接写(C++98):

Just write (C++98):

#include <vector>

typedef std::vector< std::vector<double> > matrix;
matrix name(sizeX, std::vector<double>(sizeY));

或(C++11 及更高版本):

or (C++11 and later):

#include <vector>

using matrix = std::vector<std::vector<double>>;
matrix name(sizeX, std::vector<double>(sizeY));

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