1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
pub fn homogeneous_products(
n: usize,
k: usize,
) -> Vec<Vec<usize>> {
assert!(n > 0);
let mut res = vec![];
let mut a: Vec<_> = vec![0; k];
loop {
res.push(a.clone());
let mut i = k;
for j in (0..k).rev() {
if a[j] != n - 1 {
i = j;
break;
}
}
if i == k {
return res;
}
a[i] += 1;
for j in i + 1..k {
a[j] = a[j - 1];
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test() {
let res = homogeneous_products(5, 3);
assert_eq!(
res,
[
[0, 0, 0],
[0, 0, 1],
[0, 0, 2],
[0, 0, 3],
[0, 0, 4],
[0, 1, 1],
[0, 1, 2],
[0, 1, 3],
[0, 1, 4],
[0, 2, 2],
[0, 2, 3],
[0, 2, 4],
[0, 3, 3],
[0, 3, 4],
[0, 4, 4],
[1, 1, 1],
[1, 1, 2],
[1, 1, 3],
[1, 1, 4],
[1, 2, 2],
[1, 2, 3],
[1, 2, 4],
[1, 3, 3],
[1, 3, 4],
[1, 4, 4],
[2, 2, 2],
[2, 2, 3],
[2, 2, 4],
[2, 3, 3],
[2, 3, 4],
[2, 4, 4],
[3, 3, 3],
[3, 3, 4],
[3, 4, 4],
[4, 4, 4]
]
);
}
}