扩展二维矩阵

Question

I have input matrix maze[3][3] as

asd
usd
psd

and I want to convert it into two matrix mazeW[3][4] and mazeE[3][4] of form

Wasd 
Wusd
Wpsd

and

asdE
usdE
psdE

How should I do it?? I tried this but not helping

for(int i=0;i<row;i++)
{
strcpy("W",strcpy(mazeW[i],maze[i]));
strcpy(strcpy(mazeE[i],maze[i]),"E");
}

Answer 1

If you are using strcpy function, your source string must terminate with '\\0', Seems like in your code maze[3][3] is not intended to be a array of strings as there is no space reserved for '\\0'.

In that case you cat use strcpy function instead use memcpy where you can provide the size of memory to be copied.

for ( i=0; i < row; i++ )
{
    mazeW[i][0] = 'W';
    memcpy ( mazeW[i]+1, maze[i], 3); 

    mazeE[i][3] = 'E';
    memcpy ( mazeE[i], maze[i], 3);
}

Answer 2

for(i=0;i<3;i++)
{
    mazeW[i][0] = 'W';  //sets the first element of each line to W
    memcpy(&mazeW[i][1], maze[i], sizeof(char)*3);   //copies the rest of the line from maze

    mazeE[i][3] = 'E';  // sets the last element of each line to E
    memcpy(&mazeE[i][0], maze[i], sizeof(char)*3);  ////copies the beggining of the line from maze
}

Answer 3

Without having more of your source posted, it looks and sounds like you are confusing arrays and strings.

In C and C++ a 'char' is an 8-bit value that is usually used to store an ASCII character. The ASCII table is like the periodic table, it provides a numbered list of things so that you can refer to them numerically. 1 in the periodic table is Hydrogen, it is element 1. In ASCII the value 32 represents the space character, the value 48 represents the '0' character, 49 represents '1'.

In C and C++ the convention is that if a sequence of characters are supposed to be treated as a string, they must end with a character that has the ASCII value of 0 (not '0', but 0, also written '\\0').

So store a 3-character string, you need 4 chars or bytes.

char foo[3] = "foo"; // illegal. "foo" is actually { 'f', 'o', 'o', 0 };
char bar[4] = "foo"; // ok

Because your arrays appear to be char-arrays and not strings, you cannot use "strcpy" etc, you must use "memcpy" or copy elements by hand.

Here is a working version of the problem you are trying to solve, hope this helps.

Online demo at ideone: http://ideone.com/6TcapX

#include <stdio.h>
#include <string.h>

#define MAZE_COLUMNS 3
#define MAZE_ROWS 3
#define MAZEW_COLUMNS 4
#define MAZEE_COLUMNS 4

static void transcribeMazeRow(const char* source, size_t srcColumns, char prefix, char* dest, size_t destColumns)
{
    dest[0] = prefix;
    memcpy(&dest[1], &source[0], srcColumns * sizeof(source[0]));
}

int main(int argc, char* argv[])
{
    // 3 rows of 3 columns, each is a distinct char. this is not a string.
    char maze[MAZE_ROWS][MAZE_COLUMNS] = { { 'a', 's', 'd' }, { 'u', 's', 'd' }, { 'p', 's', 'd' } };

    // 3 rows of 4 columns, distinct character values, not a string.
    char mazeW[MAZE_ROWS][MAZEW_COLUMNS];
    char mazeE[MAZE_ROWS][MAZEE_COLUMNS];

    for (size_t row = 0; row < MAZE_ROWS; ++row) {
        transcribeMazeRow(maze[row], MAZE_COLUMNS, 'W', mazeW[row], MAZEW_COLUMNS);
        transcribeMazeRow(maze[row], MAZE_COLUMNS, 'E', mazeE[row], MAZEE_COLUMNS);
    }

    // this part is mostly to show the poster the correct way to refer to all elements of each array.
    printf("maze: %c%c%c, %c%c%c, %c%c%c\n",
            maze[0][0], maze[0][1], maze[0][2],
            maze[1][0], maze[1][1], maze[1][2],
            maze[2][0], maze[2][1], maze[2][2]      );
    printf("mazeW: %c%c%c%c, %c%c%c%c, %c%c%c%c\n",
            mazeW[0][0], mazeW[0][1], mazeW[0][2], mazeW[0][3],
            mazeW[1][0], mazeW[1][1], mazeW[1][2], mazeW[1][3],
            mazeW[2][0], mazeW[2][1], mazeW[2][2], mazeW[2][3]      );
    printf("mazeE: %c%c%c%c, %c%c%c%c, %c%c%c%c\n",
            mazeE[0][0], mazeE[0][1], mazeE[0][2], mazeE[0][3],
            mazeE[1][0], mazeE[1][1], mazeE[1][2], mazeE[1][3],
            mazeE[2][0], mazeE[2][1], mazeE[2][2], mazeE[2][3]      );

    return 0;
}

Output:

maze: asd, usd, psd
mazeW: Wasd, Wusd, Wpsd
mazeE: Easd, Eusd, Epsd