spiral.c

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

typedef struct Grid {
    char *grid;
    int width;
    int height;
} Grid;

Grid *createGrid(int length)
{
    Grid *grid = malloc(sizeof(Grid));

    grid->width = length + 1;
    grid->height = length;
    grid->grid = malloc((grid->width * grid->height + 1) * sizeof(char));

    int v;
    int h;
    for (v = 0; v < grid->height; v++) {
        for (h = 0; h < (grid->width - 1); h++) {
            grid->grid[v * grid->width + h] = ' ';
        }
        grid->grid[(v + 1) * grid->width - 1] = '\n';
    }
    grid->grid[grid->height * grid->width] = '\0';
    
    return grid;
}

void printGrid(Grid *grid)
{
    printf("%s", grid->grid);
}   

void drawPoint(Grid *grid, int x, int y)
{
    grid->grid[y * (grid->width) + x] = '*';
}

void drawLine(Grid *grid, int x1, int y1, int x2, int y2)
{
    int deltaX = x2 - x1;
    int deltaY = y2 - y1;
    int i;
    if (deltaX != 0) {
        if (deltaX > 0) {
            for (i = x1; i <= x2; i++) {
                drawPoint(grid, i, y1);
            }
        } else {
            for (i = x1; i >= x2; i--) {
                drawPoint(grid, i, y1);
            }
        }
    } else {
        if (deltaY > 0) {
            for (i = y1; i <= y2; i++) {
                drawPoint(grid, x1, i);
            }
        } else {
            for (i = y1; i >= y2; i--) {
                drawPoint(grid, x1, i);
            }
        }
    }
}

typedef enum Direction {
    UP,
    RIGHT,
    DOWN,
    LEFT
} Direction;

void drawSpiral(Grid *grid, int length)
{
    int i;
    int x1 = 0;
    int y1 = 0;
    int x2;
    int y2;
    Direction direction = RIGHT;
    for (i = length - 1; i > 0; i--) {
        if (direction == RIGHT) {
            x2 = x1 + i;
            y2 = y1;
        } else if (direction == DOWN) {
            x2 = x1;
            y2 = y1 + i;
        } else if (direction == LEFT) {
            x2 = x1 - i;
            y2 = y1;
        } else if (direction == UP) {
            x2 = x1;
            y2 = y1 - i;
        }

        drawLine(grid, x1, y1, x2, y2);
       
        x1 = x2;
        y1 = y2;

        direction = (direction + 1) % 4;
    }
}


int main()
{
    Grid *grid = createGrid(32);
    //printGrid(grid);
    //drawSpiral(grid, 12);
    /*
    drawPoint(grid, 0,                  0);
    drawPoint(grid, grid->width - 2,    0);
    drawPoint(grid, 0,                  grid->height - 1);
    drawPoint(grid, grid->width - 2,    grid->height - 1);
    */
    /*
    drawLine(grid, 0, 0, 3, 0);
    drawLine(grid, 3, 3, 0, 3);
    drawLine(grid, 0, 0, 0, 3);
    drawLine(grid, 3, 0, 3, 3);
    */
    drawSpiral(grid, 32);
    printGrid(grid);

    return 0;
}