c/c++ 多维数组和指针

c/c++ 多维数组和指针

知识点

1，初始化多维数组，对应代码里的test1

2，遍历多维数组,除了最内层循环外，其他所有层都必须是引用类型，对应代码里的test2

3，指针和多维数组 ，对应代码里的test3

#include <iostream>

using namespace std;

int main(){
  //test1 初始化多维数组                                                        
  /*                                                                            
  int ia[3][4] = {                                                              
    {0,1,2,3},                                                                  
    {4,5,6,7},                                                                  
    {8,9,10,11}                                                                 
  };                                                                            
  //ia2和ia完全相同                                                             
  int ia2[3][4] = {0,1,2,3,4,5,6,7,8,9,10,11};                                  
  //只初始化每行的首元素,其他元素为默认值                                       
  int ia3[3][4] = {{1},{4},{8}};                                                
  int ia4[2][3][4] = {1};                                                       
  //用ia4的首元素为ia最后一行最后一列的最后一个元素赋值                         
  ia[2][3] = ia4[0][0][0];                                                      
  //把row绑定到ia的第二行上                                                     
  int (&row)[4] = ia[2];                                                        
  for(auto s : row){                                                            
    cout << s << ",";                                                           
  }                                                                             
  cout << endl;                                                                 
  */

  //test2 遍历多维数组,除了最内层循环外，其他所有层都必须是引用类型             
  /*                                                                           
  constexpr size_t rowcnt = 3,colcnt = 4;                                       
  int ia[3][4] = {                                                              
    {0,1,2,3},                                                                  
    {4,5,6,7},                                                                  
    {8,9,10,11}                                                                 
  };                                                                            
  for(size_t i = 0; i < rowcnt; ++i){                                           
    for(size_t j = 0; j < colcnt; ++j){                                         
      cout << ia[i][j] << ",";                                                  
    }                                                                           
    cout << endl;                                                               
  }                                                                             
  //除了最内层循环外，其他所有层都必须是引用类型                                
  for(auto &row : ia){                                                          
    for(auto &col : row){                                                       
      cout << col << ",";                                                       
    }                                                                           
    cout << endl;                                                               
  }                                                                             
  */

  //test3 指针和多维数组                                                        
  int ia[3][4] = {
    {0,1,2,3},
    {4,5,6,7},
    {8,9,10,11}
  };
  //普通遍历                                                                    
  for(auto p = ia; p != ia + 3; ++p){
    for(auto q = *p; q != *p + 4; ++q){
      cout << *q << ",";
    }
    cout << endl;
  }
  //利用库函数begin和end                                                        
  for(auto p = std::begin(ia); p != std::end(ia); ++p){
    for(auto q = std::begin(*p); q != std::end(*p); ++q){
      cout << *q << ",";
    }
    cout << endl;
  }
  //利用别名                                                                    
  using iar = int[4];
  for(iar* p = ia; p != ia + 3; ++p){
    for(int* q = *p; q != *p + 4;++q){
      cout << *q << ",";
    }
    cout << endl;
  }
}

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