dsalgo 0.2.6

A package for Datastructures and Algorithms.
Documentation 
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
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138

/// O(1)
pub fn most_significant_bit(n: usize) -> isize {
    0usize.leading_zeros() as isize - n.leading_zeros() as isize - 1
}

/// O(1)
pub fn msb_number_binary_search(mut n: usize) -> usize {
    if n & 0xffffffff00000000 > 0 {
        n &= 0xffffffff00000000;
    }
    if n & 0xffff0000ffff0000 > 0 {
        n &= 0xffff0000ffff0000;
    }
    if n & 0xff00ff00ff00ff00 > 0 {
        n &= 0xff00ff00ff00ff00;
    }
    if n & 0xf0f0f0f0f0f0f0f0 > 0 {
        n &= 0xf0f0f0f0f0f0f0f0;
    }
    if n & 0xcccccccccccccccc > 0 {
        n &= 0xcccccccccccccccc;
    }
    if n & 0xaaaaaaaaaaaaaaaa > 0 {
        n &= 0xaaaaaaaaaaaaaaaa;
    }
    n
}

pub fn least_significant_bit(n: usize) -> usize {
    n.reverse_bits().leading_zeros() as usize
}

pub fn lsb_number(n: usize) -> usize {
    let n = n as isize;
    (n & -n) as usize
}

pub fn delete_least_bit(n: usize) -> usize { n - lsb_number(n) }

pub fn delete_least_bit_v2(n: usize) -> usize { n & (n - 1) }

/// O(1)
pub fn bit_length(n: usize) -> usize {
    (0usize.leading_zeros() - n.leading_zeros()) as usize
}

/// O(1)
pub fn bit_length_v2(mut n: usize) -> usize {
    if n == 0 {
        return 0;
    }
    let mut l = 1;
    for i in (0..6usize).rev() {
        if n >> (1 << i) > 0 {
            n >>= 1 << i;
            l += 1 << i;
        }
    }
    l
}

/// O(\log{N})
pub fn bit_length_v3(n: usize) -> usize {
    let mut l = 0usize;
    while 1 << l <= n {
        l += 1;
    }
    l
}

/// O(N)
pub fn bit_length_table(n: usize) -> Vec<usize> {
    let mut l = vec![0; n];
    for i in 1..n {
        l[i] = l[i >> 1] + 1;
    }
    l
}

/// O(1)
pub fn reverse_bits(n: usize) -> usize { n.reverse_bits() }

/// O(1)
pub fn reverse_bits_v2(mut n: usize) -> usize {
    n = ((n & 0xaaaaaaaaaaaaaaaa) >> 1) | ((n & 0x5555555555555555) << 1);
    n = ((n & 0xcccccccccccccccc) >> 2) | ((n & 0x3333333333333333) << 2);
    n = ((n & 0xf0f0f0f0f0f0f0f0) >> 4) | ((n & 0x0f0f0f0f0f0f0f0f) << 4);
    n = ((n & 0xff00ff00ff00ff00) >> 8) | ((n & 0x00ff00ff00ff00ff) << 8);
    n = ((n & 0xffff0000ffff0000) >> 8) | ((n & 0x0000ffff0000ffff) << 16);
    (n >> 32) | (n << 32)
}

/// O(1)
pub fn bit_inverse(n: usize) -> usize { !n }

/// O(1)
pub fn bit_inverse_v2(n: usize) -> usize { (!0usize) ^ n }

/// O(1)
pub fn popcount(mut n: usize) -> usize {
    n -= (n >> 1) & 0x5555555555555555;
    n = (n & 0x3333333333333333) + ((n >> 2) & 0x3333333333333333);
    n = (n + (n >> 4)) & 0x0f0f0f0f0f0f0f0f;
    n = n + (n >> 8);
    n = n + (n >> 16);
    n = n + (n >> 32);
    return n & 0x0000007f;
}

/// O(1)
pub fn popcount_v2(n: usize) -> usize { n.count_ones() as usize }

/// O(\log{N})
pub fn popcount_v3(mut n: usize) -> usize {
    let mut cnt = 0usize;
    while n > 0 {
        cnt += n & 1;
        n >>= 1
    }
    cnt
}

/// O(N)
pub fn popcount_table(n: usize) -> Vec<usize> {
    let mut cnt = vec![0; n];
    for i in 1..n {
        cnt[i] = cnt[i >> 1] + (i & 1);
    }
    cnt
}

#[cfg(test)]
mod tests {
    #[test]
    fn bitset() {
        println!("{}", super::least_significant_bit(0));
    }
}