Thread: 3D Array - Printing Certain Rows in Order

You'll need read in the entire number and then print the top row of all of them, then the next row, then the last row.

BTW, you could define your numbers like this (which looks a lot nicer! ) :

Code:

const char segments[10][3][3] =
{
    {" _ ",
     "| |",
     "|_|"},
    {"   ",
     "  |",
     "  |"},
    {" _ ",
     " _|",
     "|_ "},
    ...
};

I like the change in structure.

Interestingly, C allows a special case of initializing a char array from a string literal while leaving off the zero-terminator. E.g., char a[4] = "1234" leaves off the terminator but doesn't cause a warning even though "1234" actually has 5 chars. But you couldn't do char a[3] = "1234" without a warning, for example.

BTW, it can be shrunk even more. "%.3s" only prints the first 3 chars.

Code:

#include <stdio.h>

const char seg[3][30] = {
  {" _     _  _     _  _  _  _  _ "},
  {"| |  | _| _||_||_ |_   ||_||_|"},
  {"|_|  ||_  _|  | _||_|  ||_|  |"}
};

int main() {
    int row, dig = 2;
    for (row = 0; row < 3; row++)
        printf("%.3s\n", seg[row] + dig * 3);
    return 0;
}

@algorism Yeah, that 2D array looks much cleaner and easier to iterate through, but unfortunately my array being 3D is a requirement.

So here's where my code stands. As it is, it is fully functional, except for one thing:

Code:

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


void seven_segment();
const char segments[3][11][4] =
{
   {" _ ", "   ", " _ ", " _ ", "   ", " _ ", " _ ", " _ ", " _ ", " _ ", "   "},
   {"| |", "  |", " _|", " _|", "|_|", "|_ ", "|_ ", "  |", "|_|", "|_|", " _ "},
   {"|_|", "  |", "|_ ", " _|", "  |", " _|", "|_|", "  |", "|_|", "  |", "   "},
};


int main(void)
{
    char YorN;
    for(;;)
    {
        seven_segment();
        printf("Please enter Y or N if you wish to continue or exit, respectively: ");
        scanf(" %c", &YorN);
        if(YorN == 'Y' | YorN == 'y')
            continue;
        else if(YorN == 'N' | YorN == 'n')
        {
            printf("Thanks for using my program!");
            exit(0);
        }
        else
        {
            while(YorN != 'Y' && YorN != 'N' && YorN != 'y' && YorN != 'n')
            {
                printf("Sorry, that was not a valid input.  Please enter Y or N: ");
                scanf(" %1c", &YorN);
                if(YorN == 'N' | YorN == 'n')
                {
                    printf("Thanks for using my program!");
                    exit(0);
                }
            }
            continue;
        }
    }
    return 0;
}


void seven_segment()
{
    int userInput, i, j;


    printf("Please enter a number to display: ");
    scanf("%d", &userInput);


    char intLength[25];
    sprintf(intLength, "%d", userInput);


    for(i=0; i<3; i++)
    {
        for(j=0; j<strlen(intLength); j++)
        {
            printf("%s ", segments[i][intLength[j]-'0']);
        }
        putchar('\n');
    }
}

How would I best implement adding a negative sign in front of negative integers?

I've added in an extra column for the negative sign, but am unsure how to iterate to it through my nested for loop correctly.

My previous attempt looked like this:

Code:

if(j = 0 && userInput < 0)
printf("%s ", segments[i][11]);

But this yielded an infinite loop.

Sorry for the confusion, and thanks again for any advice!

Firstly, remember that the index of your negative sign is 10, not 11.

I would make the interface for seven_segment take an int (or a long (or long long)), read the number in main and pass it in. That seems more natural to me.

For the negative sign, maybe something like this:

Code:

#define BASE 10
#define ROWS  3
  
void seven_segment(long n);

const char segments[ROWS][BASE+1][4] =
{
  {" _ ","   "," _ "," _ ","   "," _ "," _ "," _ "," _ "," _ ","  "},
  {"| |","  |"," _|"," _|","|_|","|_ ","|_ ","  |","|_|","|_|"," _"},
  {"|_|","  |","|_ "," _|","  |"," _|","|_|","  |","|_|","  |","  "}
};

// main ...

void seven_segment(long n) {
    int row, digit;
    char str[32];
    int len = sprintf(str, "%ld", n);

    for (row = 0; row < ROWS; row++) {
        for (digit = 0; digit < len; digit++) {
            int value = str[digit] == '-' ? BASE : str[digit] - '0';
            printf("%s ", segments[row][value]);
        }
        putchar('\n');
    }
}

Also, I removed the space to the right of the negative sign picture (in the segments array) so that it was a little closer to the first digit. You might not want to do that.

Hey everyone, thanks again for the help.

@WoodSTokk- Thanks for catching this typo. Certainly a sign of my inexperience I appreciate it.

@algorism - That makes so much sense! You also taught me about the ?: operator I didn't use it here for the sake of simplicity's sake (and the fact we haven't learnt it) but will certainly try to do so in my future C endeavours.

Implementing a separate int makes it so much easier. Here's where my code currently stands (functional atm):

Code:

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


#define DIGITS 10


void seven_segment();
const char segments[3][DIGITS + 1][4] =
{
   {" _ ", "   ", " _ ", " _ ", "   ", " _ ", " _ ", " _ ", " _ ", " _ ", "   "},
   {"| |", "  |", " _|", " _|", "|_|", "|_ ", "|_ ", "  |", "|_|", "|_|", " __"},
   {"|_|", "  |", "|_ ", " _|", "  |", " _|", "|_|", "  |", "|_|", "  |", "   "},
};


int main(void)
{
    char YorN;
    for(;;)
    {
        seven_segment();
        printf("Please enter Y or N if you wish to continue or exit, respectively: ");
        scanf(" %c", &YorN);
        if(YorN == 'Y' || YorN == 'y')
            continue;
        else if(YorN == 'N' || YorN == 'n')
        {
            printf("Thanks for using my program!");
            exit(0);
        }
        else
        {
            while(YorN != 'Y' && YorN != 'N' && YorN != 'y' && YorN != 'n')
            {
                printf("Sorry, that was not a valid input.  Please enter Y or N: ");
                scanf(" %1c", &YorN);
                if(YorN == 'N' || YorN == 'n')
                {
                    printf("Thanks for using my program!");
                    exit(0);
                }
            }
            continue;
        }
    }
    return 0;
}


void seven_segment()
{
    int userInput, i, j;


    printf("Please enter a number to display: ");
    scanf("%d", &userInput);


    char intLength[25];
    sprintf(intLength, "%d", userInput);


    for(i=0; i<3; i++)
    {
        for(j=0; j<strlen(intLength); j++)
        {
            int number = intLength[j];
            if(number == '-')
                number = DIGITS;
            else
                number = intLength[j] - '0';
            printf("%s ", segments[i][number]);
        }
        putchar('\n');
    }
}

Your main is a little overly-complicated. Maybe something like this (not perfect, but better) :

Code:

int main(void) {
    char answer;
    int c;

    for(;;) {
        seven_segment();

        for (;;) {
            printf("Do you want to do another number (Y/N)?: ");
            scanf(" %c", &answer);

            if (answer == 'N' || answer == 'n') {
                printf("Thanks for using my program!\n");
                exit(0);
            }

            // eat newline (and any extra characters)
            while ((c = getchar()) != '\n')
                ;

            if (answer == 'Y' || answer == 'y')
                break;

            printf("That was not a valid input. Try again.\n");
        }
    }

    return 0;
}