farey.c

#include <stdio.h>
// Pyörivän pyyhkäisyn kokonaisluku koordinaatit Fareyn jonosta
// https://en.wikipedia.org/wiki/Farey_sequence
// n = 5
// (0, 1)
// (1, 5)
// (1, 4)
// (1, 3)
// (2, 5)
// (1, 2)
// (3, 5)
// (2, 3)
// (3, 4)
// (4, 5)
// (1, 1)
// (5, 4)
// (4, 3)
// (3, 2)
// (5, 3)
// (2, 1)
// (5, 2)
// (3, 1)
// (4, 1)
// (5, 1)
// (1, 0)
#define swap(a,b) do{int t = a; a = b; b = t;} while(0)
int main() {
    int n = 5;
    int a = 0;
    int b = 1;
    int c = 1;
    int d = n;
    printf("(%d, %d)\n", a, b);
    while (c <= n) {
        int k = (n + b) / d;
        a = k * c - a;
        b = k * d -b;
        swap(a,c);
        swap(b,d);
        printf("(%d, %d)\n", a, b);
    }
    a = 1;
    b = 1;
    c = n - 1;
    d = n;
    while (a > 0) {
        int k = (n + b) / d;
        a = k * c - a;
        b = k * d -b;
        swap(a,c);
        swap(b,d);
        printf("(%d, %d)\n", b, a);
    }
}