从 C++ 中的函数返回向量或数组

Posted 2023-02-21

【中文标题】从 C++ 中的函数返回向量或数组

【英文标题】：Return a vector or array from a function in C++

【发布时间】：2016-05-06 05:10:14

【问题描述】：

我想创建一个程序，根据用户输入创建 N 矩阵，但我需要返回向量（或数组）值，然后将它们发送到函数，然后再次通过返回向量来获取。

例如：

vector<int> createMatrix(rows, cols)
    for(int x = 0; x < rows; x++)
        for(int y = 0; y < cols; y++)
            cout << "Please, input the values for the row " << x << " and col " << y << endl;
            vector<int> Matrix(...)values;
            cin >> (...);
        
    
return Matrix; //here is the point


vector<int> mathOperations(operation, matrixA, matrixB)
    (...)
    return vector<int> resultMatrix;


int main(int argc, char *argv[])
    int nMatrix, nRows, nCols;
    cout << "Please, answer how many matrix would you like do be created?" << endl;
    cin >> nMatrix;
    cout << "Thank you, and how many rows your matrix will have?" << endl;
    cin >> nRows;
    cout << "Thank you again, and how many cols?" << endl;
    cin >> nCols;
    cout << "Okey, creating " << nMatrix << " nMatrix for you!" << endl;

    for(int n = 0; n < nMatrix; n++)
        cout << "Please, insert the values for the matrix no" << n+1 << endl;
        vector<int> myMatrix[n] = createMatrix(nRows, nCols);
    

    /* the rest of my code with functions to print values, create a new vectors by math operations between given arguments
    */

return 0;

最好的方法是什么？

【参考方案1】：

如果您正在寻找一种使用vector 构造二维结构的方法，请使用以下内容：

#include <vector>
#include <iostream>

using std::vector;
using std::cout;
using std::cin;

typedef vector<vector<int> > matrix_t;

matrix_t createMatrix(int rows, int cols)
  matrix_t Matrix(rows, vector<int>(cols));

  for(int x = 0; x < rows; x++)
    for(int y = 0; y < cols; y++)
      cout << "Please, input the values for the row "
        << x << " and col " << y << std::endl;
      cin >> Matrix[x][y];
    
  
  return Matrix;


int main(int argc, char const* argv[])

  matrix_t M(createMatrix(2, 2));

  for (int i = 0; i < 2; i++) 
    for (int j = 0; j < 2; j++) 
      cout << M[i][j] << std::endl;
    

  

  return 0;

【讨论】：

@juanchopanza，是的，reserve 不会改变矢量的大小，所以我需要resize。修复了答案

好的，我现在将移除 cmets。顺便提一句。您可以通过像这样初始化向量来跳过调整大小循环：matrix_t Matrix(rows, vector<int>(cols));。请参阅我对this old question 的回复。

@juanchopanza，啊，确实，我们可以传递一个向量作为初始项值。