將2d向量初始化爲類變量C++

Question

我正在構建一個類，其中一個變量是一個2d向量。我如何設置它，以便我有一個初始大小？我嘗試了下面的內容，但在數字常量之前得到一個錯誤，預計'，'或'...'。另外我得到每一行的錯誤，我嘗試設置一個值爲pncode，數組下標爲無效類型'[int]'。

這裏的類：

#ifndef POSTNET_H_ 
#define POSTNET_H_ 

#include <iostream> 
#include <cstdlib> 
#include <string> 
#include <vector> 
using namespace std; 

class postnet 
{ 
private: 
    vector<vector<int>> pncode(5, vector<int>(5)); 
    void encode(vector<int> zip) 
    { 
     for(int i = 0; i < 5; i++) 
     { 
      if(zip[i] == 1 || zip[i] == 2 || zip[i] == 3 || zip[i] == 4 || zip[i] == 5 || zip[i] == 6) 
       pncode[i][0] = 0; 
      else 
       pncode[i][0] = 1; 

      if(zip[i] == 1 || zip[i] == 2 || zip[i] == 3 || zip[i] == 7 || zip[i] == 8 || zip[i] == 9) 
       pncode[i][1] = 0; 
      else 
       pncode[i][1] = 1; 
      if(zip[i] == 1 || zip[i] == 4 || zip[i] == 5 || zip[i] == 7 || zip[i] == 8 || zip[i] == 0) 
       pncode[i][0] = 0; 
      else 
       pncode[i][0] = 1; 
      if(zip[i] == 2 || zip[i] == 4 || zip[i] == 6 || zip[i] == 7 || zip[i] == 9 || zip[i] == 0) 
       pncode[i][0] = 0; 
      else 
       pncode[i][0] = 1; 
      if(zip[i] == 3 || zip[i] == 5 || zip[i] == 6 || zip[i] == 8 || zip[i] == 9 || zip[i] == 0) 
       pncode[i][0] = 0; 
      else 
       pncode[i][0] = 1; 
     } 
    } 
    void decode(vector<int> zip) 
    { 
     int zipd[5]; 

     for(int i = 0; i < 5; i++) 
     { 
      zipd[0] = pncode[i][0] * 7; 
      zipd[1] = pncode[i][1] * 4; 
      zipd[2] = pncode[i][2] * 2; 
      zipd[3] = pncode[i][3] * 1; 
      zipd[4] = pncode[i][4] * 0; 

      for(int j = 0; j < 5; j++) 
      { 
       zip[i] += zipd[j]; 
      } 
      if(zip[i] == 11) 
       zip[i] = 0; 
     } 
    } 

public: 
    postnet() 
    { 
     for(int i = 0; i < 5; i++) 
      for(int j = 0; j < 5; j++) 
       pncode[i][j] = 0; 
    } 
    postnet(vector<int> zip) 
    { 
     encode(zip); 
    } 
    postnet(vector<vector<int> > pnc) 
    { 
     for(int i = 0; i < 5; i++) 
      for(int j = 0; j < 5; j++) 
       pncode[i][j] = pnc[i][j]; 
    } 
    void print_zip() 
    { 
     vector<int> zipc(5); 
     decode(zipc); 

     for(int i = 0; i < 5; i++) 
      cout << zipc[i]; 

     cout << endl; 
    } 

    void print_pncode() 
    { 
     cout << "1"; 
     for(int i = 0; i < 5; i++) 
      for(int j = 0; j < 5; j++) 
       cout << pncode[i][j]; 
     cout << "1" << endl; 
    } 

}; 


#endif /* POSTNET_H_ */ 

Answer 1

你現在使用的代碼，vector<vector<int>> pncode(5, vector<int>(5));，就足夠了C++編譯器11。在此之前，您必須在您的構造函數中初始化pncode。 （您可能還需要在尖括號之間添加空格; >>。）

postnet(vector<int> const &zip) 
    : pncode(5, vector<int>(5)) 
{ 
    encode(zip); 
} 
postnet(vector<vector<int> > const &pnc = vector<vector<int> >(5, vector<int>(5))) 
{ 
    assert(pnc.size()==5); 
    for (int i=0;i<pnc.size();++i) 
     assert(pnc[i].size()==5); 

    pncode = pnc; 
} 

我還帶着一個缺省參數替代默認的構造函數，改變參數類型爲const &，並消除了自由手動複製矢量元素。