In [1]:
```get_ipython().ast_node_interactivity = 'all'

import matplotlib.pyplot as plt
import numpy as np```
In [2]:
```def rot(n, x, y, rx, ry):
if ry == 0:
if rx == 1:
x = (n - 1) - x
y = (n - 1) - y

t = x
x = y
y = t
return x, y```
In [3]:
```def xy2d(n, x, y):
rx = 0
ry = 0
s = int(n / 2)
d = 0

while s > 0:
rx = int((x & s) > 0)
ry = int((y & s) > 0)
d += s * s * ((3 * rx) ^ ry)
x, y = rot(n, x, y, rx, ry)
s //= 2

return d```
In [4]:
```for x in range(10):
for y in range(10):
print(xy2d(50, x, y))```
Out:
```0
635
45
754
488
815
488
815
769
799
1905
1270
2364
1367
2373
1450
2364
1450
1404
1414
128
682
90
718
524
860
524
860
897
887
2076
1306
2256
1342
2256
1486
2256
1486
1523
1511
180
1103
245
1148
360
995
389
995
1041
1031
2085
1718
2265
1783
2265
1630
2265
1630
1676
1646
189
1103
234
1148
369
1004
378
1004
1041
1031
2076
1727
2256
1772
2256
1630
2256
1630
1667
1655
2039
1712
2280
1800
2271
1584
2280
1584
1538
1568
2029
1682
2292
1810
2301
1594
2292
1594
1548
1558
```
In [5]:
```"""
//convert (x,y) to d
int xy2d (int n, int x, int y) {
int rx, ry, s, d=0;
for (s=n/2; s>0; s/=2) {
rx = (x & s) > 0;
ry = (y & s) > 0;
d += s * s * ((3 * rx) ^ ry);
rot(n, &x, &y, rx, ry);
}
return d;
}

//convert d to (x,y)
void d2xy(int n, int d, int *x, int *y) {
int rx, ry, s, t=d;
*x = *y = 0;
for (s=1; s<n; s*=2) {
rx = 1 & (t/2);
ry = 1 & (t ^ rx);
rot(s, x, y, rx, ry);
*x += s * rx;
*y += s * ry;
t /= 4;
}
}

void rot(int n, int *x, int *y, int rx, int ry) {
if (ry == 0) {
if (rx == 1) {
*x = n-1 - *x;
*y = n-1 - *y;
}

//Swap x and y
int t  = *x;
*x = *y;
*y = t;
}
}
"""```
Out [5]:
`'\n//convert (x,y) to d\nint xy2d (int n, int x, int y) {\n    int rx, ry, s, d=0;\n    for (s=n/2; s>0; s/=2) {\n        rx = (x & s) > 0;\n        ry = (y & s) > 0;\n        d += s * s * ((3 * rx) ^ ry);\n        rot(n, &x, &y, rx, ry);\n    }\n    return d;\n}\n\n//convert d to (x,y)\nvoid d2xy(int n, int d, int *x, int *y) {\n    int rx, ry, s, t=d;\n    *x = *y = 0;\n    for (s=1; s`