2D阵列的动力分配

Question

谁能告诉我这个代码片断，请的描述？

chessBoard = new char*[ tRows ] ;
for ( unsigned int c = 0; c < rows; c++ )
{
    chessBoard[ c ] = new char[ columns ];
}

问题：

什么是char*[tRows]，什么是它的效果？ 而且，什么是chessBoard[c]？

请给我确切的描述。

Answer 1

char *chessBoard  = new char[ tRows ] ; //correct definition
//chessBoard is a pointer to array of tRow size of characters

for( unsigned int c = 0 ;   c < rows ;   c++ )
chessBoard[ c ] = new char[ columns ] ;
//we assign each row with a constant number of columns

正如你已经知道棋盘基本可以表示为一个方阵，因此

Matrix dimension: Row x Column where Row = Column

希望这能回答你的问题！

干杯，

了Arul Verman

Answer 2

尽管你可以自由地声明和分配用于一个阵列的指针到char [tRows]，然后循环分配用于每行，也可以声明一个指针的char [tRows]的阵列，并在单个呼叫，其提供分配他们的tRows一个分配的效益和单个自由，如

#include <iostream>
#include <iomanip>

#define tRows 10

int main (void) {

    char (*chessboard)[tRows] = new char[tRows][tRows];

    for (int i = 0; i < tRows; i++) {
        for (int j = 0; j < tRows; j++) {
            chessboard[i][j] = i + j;
            std::cout << " " << std::setw(2) << (int)chessboard[i][j];
        }
        std::cout << '\n';
    }

    delete[] (chessboard);
}

实施例使用/输出

$ ./bin/newdelete2d
  0  1  2  3  4  5  6  7  8  9
  1  2  3  4  5  6  7  8  9 10
  2  3  4  5  6  7  8  9 10 11
  3  4  5  6  7  8  9 10 11 12
  4  5  6  7  8  9 10 11 12 13
  5  6  7  8  9 10 11 12 13 14
  6  7  8  9 10 11 12 13 14 15
  7  8  9 10 11 12 13 14 15 16
  8  9 10 11 12 13 14 15 16 17
  9 10 11 12 13 14 15 16 17 18

并且，确认您的内存使用：

$ valgrind ./bin/newdelete2d
==7838== Memcheck, a memory error detector
==7838== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==7838== Using Valgrind-3.12.0 and LibVEX; rerun with -h for copyright info
==7838== Command: ./bin/newdelete2d
==7838==
  0  1  2  3  4  5  6  7  8  9
  1  2  3  4  5  6  7  8  9 10
  2  3  4  5  6  7  8  9 10 11
  3  4  5  6  7  8  9 10 11 12
  4  5  6  7  8  9 10 11 12 13
  5  6  7  8  9 10 11 12 13 14
  6  7  8  9 10 11 12 13 14 15
  7  8  9 10 11 12 13 14 15 16
  8  9 10 11 12 13 14 15 16 17
  9 10 11 12 13 14 15 16 17 18
==7838==
==7838== HEAP SUMMARY:
==7838==     in use at exit: 0 bytes in 0 blocks
==7838==   total heap usage: 2 allocs, 2 frees, 72,804 bytes allocated
==7838==
==7838== All heap blocks were freed -- no leaks are possible
==7838==
==7838== For counts of detected and suppressed errors, rerun with: -v
==7838== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)