Displaying text pyramid from topographic view

Question

I write in C on arduino uno. The idea is to display pyramid from topographic view so variables that I have is the 'seedP' - middle value, the size of pyramid 'sizeP' - the amount of layers and how many letters are in a row - 'layer'.

The pyramid with those values in the code seedP = 6, sizeP = 3 would look like:

44444
45554
45654
45554
44444

Here is the code:

void setup()
   {
     Serial.begin(9600);
     int seedP = 6; //Centre value
     int sizeP = 3; //Amount of layers
     int layer = (sizeP*2)-1;

     for(int i=0; i<layer; i++){
       for(int j=0; j<layer; j++){
           Serial.print(seedP);
       }
       Serial.println();
     }
   }

I still cannot fully grasp the concept of the algorithm I could potentially check for first and last layer then display a value full of '4' in this example but I'm not sure how to deal with other layers. The code right now displays only '6'es in 5 columns and 5 in a row.

Edit: Updated code and below is the grid

void setup()
   {
     Serial.begin(9600);

     int sizeP = 3; //Amount of layers
     int layer = (sizeP*2)-1;

     int seedP = 6; //Centre value
     int seedX = sizeP-1;
     int seedY = sizeP-1;

     for(int i=0; i<layer; i++){
       for(int j=0; j<layer; j++){
           //i,j = x,y grid
           int distanceX, distanceY, distance; //Distance between a cell and center value
           distanceX = abs(seedX - j);
           distanceY = abs(seedY - i);
           distance = distanceX + distanceY;
       }
       Serial.println();
     }
   }

Values from each cell to the center

(0,0)=4, (0,1)=3,   (0,2)=2,  (0,3)=3,  (0,4)=4
(1,0)=3, (1,1)=2,   (1,2)=1,  (1,3)=2,  (1,4)=3
(2,0)=2, (2,1)=1,   (2,2)=0,  (2,3)=1,  (2,4)=2
(3,0)=3, (3,1)=2,   (3,2)=1,  (3,3)=2,  (3,4)=3
(4,0)=4, (4,1)=3,   (4,2)=2,  (4,3)=3,  (4,4)=4

Answer 1

Nice puzzle, here is my suggestion:

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

/* get the depth relative to the pyramids center, which is at origo */
int depth(int x, int y)
{
    x = abs(x);
    y = abs(y);

    return x > y ? x : y;
}

/* walk from (-(size - 1), size - 1) along the x and y axis, and print
 * the center value minus the current depth */
void pyramid(char center, int size)
{
    int x, y;

    size--;

    for (x = -size; x <= size; x++) {
        for (y = -size; y <= size; y++)
            putchar(center - depth(x, y));
        putchar('\n');
    }
}

int main(int argc, char **argv)
{
    char seedP = argv[1][0];
    int sizeP = strtol(argv[2], NULL, 0);

    pyramid(seedP, sizeP);
}

Note that there is no error handling of any kind here, you'd better run it with two arguments.

Example:

$ gcc pyramid.c -o pyramid && ./pyramid 6 7
0000000000000
0111111111110
0122222222210
0123333333210
0123444443210
0123455543210
0123456543210
0123455543210
0123444443210
0123333333210
0122222222210
0111111111110
0000000000000