#include <stdio.h>
   int grid[5*5] = {0};
   typedef struct pt {
     int x;
     int y;
   } pt;
   void plot(pt p)
   {
     grid[p.x+p.y*5] = 1;
   }
   pt pt1 = {2,1};
   pt pt2 = {4,3};
   pt pt3 = {0,3};
   void line(pt a, pt b)
   {
     pt change = {b.x - a.x, b.y - a.y};
     int ctx = change.x > 0 ? change.x : -change.x;
     int cty = change.y > 0 ? change.y : -change.y;
     int ct = ctx > cty ? ctx : cty;
     for (int t = 0; t <= ct; ++ t) {
       pt p = {a.x + change.x * t / ct, a.y + change.y * t / ct};
       plot(p);
     }
   }
   int main()
   {
     line(pt1, pt2);
     line(pt2, pt3);
     line(pt3, pt1);
     for (int y = 0; y < 5; y ++) {
       for (int x = 0; x < 5; x ++)
         printf("%d", grid[x + y * 5]);
       printf("\n");
     }
   }