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
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164

pub mod bitset {
    use std::ops::{BitOrAssign, Shl};
    const ONE_VALUE_LENGTH: usize = 60;
    const MAXIMUM: u64 = (1 << ONE_VALUE_LENGTH) - 1;

    pub fn get_bit_position(index: usize) -> (usize, usize) {
        let data_index = index / ONE_VALUE_LENGTH;
        let bit_index = index % ONE_VALUE_LENGTH;
        (data_index, bit_index)
    }

    #[derive(PartialEq, Clone, Debug)]
    pub struct BitSet {
        data: Vec<u64>,
    }

    impl BitOrAssign for BitSet {
        fn bitor_assign(&mut self, rhs: Self) {
            if self.data.len() < rhs.data.len() {
                self.data.resize(rhs.data.len(), 0);
            }
            let n = if self.data.len() > rhs.data.len() {
                rhs.data.len()
            } else {
                self.data.len()
            };
            for i in 0..n {
                assert!(self.data[i] <= MAXIMUM);
                assert!(rhs.data[i] <= MAXIMUM);
                self.data[i] |= rhs.data[i];
            }
        }
    }

    impl Shl<usize> for BitSet {
        type Output = Self;
        fn shl(self, rhs: usize) -> Self {
            self.shift_left(rhs)
        }
    }

    impl BitSet {
        pub fn new(n: usize) -> Self {
            let size = (n + ONE_VALUE_LENGTH - 1) / ONE_VALUE_LENGTH;
            BitSet {
                data: vec![0; size],
            }
        }

        pub fn new_from(value: u64) -> Self {
            BitSet { data: vec![value] }
        }

        pub fn set(&mut self, index: usize, value: bool) {
            let (data_index, bit_index) = get_bit_position(index);
            assert!(self.data.len() > data_index);
            if value {
                self.data[data_index] |= 1 << bit_index;
            } else {
                let tmp = MAXIMUM ^ (1 << bit_index);
                self.data[data_index] &= tmp;
            }
        }

        pub fn get(&mut self, index: usize) -> bool {
            let (data_index, bit_index) = get_bit_position(index);
            assert!(self.data.len() > data_index);
            self.data[data_index] & (1 << bit_index) != 0
        }

        pub fn shift_left(&self, shift: usize) -> Self {
            let mut next_data = Vec::new();
            let prefix_empty_count = shift / ONE_VALUE_LENGTH;
            let shift_count = shift % ONE_VALUE_LENGTH;
            for _ in 0..prefix_empty_count {
                next_data.push(0);
            }

            let mut from_previous = 0;
            let room = ONE_VALUE_LENGTH - shift_count;
            for &data in self.data.iter() {
                let overflow = (data >> room) << room;
                let rest = data - overflow;
                let value = (rest << shift_count) + from_previous;
                assert!(value <= MAXIMUM);
                next_data.push(value);
                from_previous = overflow >> room;
            }
            if from_previous > 0 {
                next_data.push(from_previous);
            }
            BitSet { data: next_data }
        }
    }
}

#[cfg(test)]
mod test {
    use super::bitset::*;
    use test::Bencher;

    #[test]
    fn test_set_bit() {
        let n = 10;
        let value = 717;
        let mut bitset = BitSet::new(n);
        for i in 0..n {
            if value & (1 << i) != 0 {
                bitset.set(i, true);
            }
        }

        for i in 0..n {
            if value & (1 << i) != 0 {
                assert!(bitset.get(i));
            } else {
                assert!(!bitset.get(i));
            }
        }
    }

    #[test]
    fn test_bitset_or() {
        let mut value1 = 717;
        let mut bitset1 = BitSet::new_from(value1);

        let value2 = 127;
        let bitset2 = BitSet::new_from(value2);

        value1 |= value2;
        bitset1 |= bitset2;

        for i in 0..50 {
            if value1 & (1 << i) != 0 {
                assert!(bitset1.get(i));
            } else {
                assert!(!bitset1.get(i));
            }
        }
    }

    #[test]
    fn test_bitset_shift_left() {
        let value1 = 717;
        let first_shift = 30;
        let second_shift = 40;
        let bitset1 = BitSet::new_from(value1) << (first_shift + second_shift);
        let bitset2 = BitSet::new_from(value1 << first_shift) << second_shift;
        assert!(bitset1 == bitset2);
    }

    #[bench]
    fn bench_bitset(b: &mut Bencher) {
        let n = 2000;
        b.iter(|| {
            let mut set = BitSet::new(n);
            for i in 1..=n {
                let next = set.shift_left(i);
                set |= next;
            }
            set
        })
    }
}