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  1. #include <stdio.h>
  2. //convert (x,y) to d
  3. int xy2d (int n, int x, int y) {
  4.     int rx, ry, s, d=0;
  5.     for (s=n/2; s>0; s/=2) {
  6.         rx = (x & s) > 0;
  7.         ry = (y & s) > 0;
  8.         d += s * s * ((3 * rx) ^ ry);
  9.         rot(s, &x, &y, rx, ry);
  10.     }
  11.     return d;
  12. }
  13.  
  14. //convert d to (x,y)
  15. void d2xy(int n, int d, int *x, int *y) {
  16.     int rx, ry, s, t=d;
  17.     *x = *y = 0;
  18.     for (s=1; s<n; s*=2) {
  19.         rx = 1 & (t/2);
  20.         ry = 1 & (t ^ rx);
  21.         rot(s, x, y, rx, ry);
  22.         *x += s * rx;
  23.         *y += s * ry;
  24.         t /= 4;
  25.     }
  26. }
  27.  
  28. //rotate/flip a quadrant appropriately
  29. void rot(int n, int *x, int *y, int rx, int ry) {
  30.     if (ry == 0) {
  31.         if (rx == 1) {
  32.             *x = n-1 - *x;
  33.             *y = n-1 - *y;
  34.         }
  35.  
  36.         //Swap x and y
  37.         int t  = *x;
  38.         *x = *y;
  39.         *y = t;
  40.     }
  41. }
  42. int main(void) {
  43. 	int x = 0;
  44. 	int y = 0;
  45. 	d2xy(1000, 228, &x, &y);
  46. 	printf("%d %d", x,y);
  47. }
  48.  
Runtime error #stdin #stdout 0s 2292KB
comments (?)
stdin 
asd
stdout 
9 3
https://ideone.com/M9cYkm
language:
C (gcc 8.3)
created:
9 years ago
visibility:
public

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