c++ std::bitset

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作用：
及  64位 移位  取或  用64个位存储64个位，取 或 merge 。 然后查索引即知道id是否存在~~           目标：省空间。

#include <iostream>
#include <bitset>
#include <string>
using namespace std;

int main(){

    //bitset<n> b;//b有n位，每位都为0 
    bitset<16> bitvec;
    cout << bitvec << endl;

    //bitset<n> b(u); //b是unsigned long型u的一个副本
    bitset<16> bitvec2(0xffff);
    cout << bitvec2 << endl;
    
    bitset<128> bitvec3(0xffff);
    cout << bitvec3 << endl;

    //bitset<n> b(s); //b是string对象s中含有的位串的副本 
    string strval("1100");
    bitset<32> bitvec4(strval);
    cout << bitvec4 << endl;

    string str("1111111000000011001101"); 
    //bitset<n> b(s, pos, n);//b是s中从位置pos开始的n个位的副本
    bitset<32> bitvec5(str, 5, 4);
    cout << bitvec5 << endl;
    bitset<32> bitvec6(str, str.size() - 4);
    cout << bitvec6 << endl;

    cout << sizeof(unsigned long) << endl;

    //unsigned long a = 1;
    //unsigned long b = a << 63;
    uint64_t a = 1;
    uint64_t b = a << 63;
    bitset<64> vec(b);
    cout << vec << endl;
    return 0;
}

output:

0000000000000000 16
1111111111111111 16
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001111111111111111 128
00000000000000000000000000001100 32
00000000000000000000000000001100 32
00000000000000000000000000001101 32
8 1
1000000000000000000000000000000000000000000000000000000000000000 64

-------------------------------------------

#include <iostream>
#include <stdint.h>
#include <bitset>
using namespace std;


int main() {
    for(int i=0; i<64; i++){
        uint64_t a = 1;
        uint64_t b = a << i;
        bitset<64> bs(b);
        cout << i << " 	" << bs << "," << bs.to_ulong() << endl;
    }
    bitset<64> sum_bin;
    sum_bin.set();
    cout << "	" << sum_bin << "," << sum_bin.to_ulong() << endl;

    return 0;
}

0     0000000000000000000000000000000000000000000000000000000000000001,1
1     0000000000000000000000000000000000000000000000000000000000000010,2
2     0000000000000000000000000000000000000000000000000000000000000100,4
3     0000000000000000000000000000000000000000000000000000000000001000,8
4     0000000000000000000000000000000000000000000000000000000000010000,16
5     0000000000000000000000000000000000000000000000000000000000100000,32
6     0000000000000000000000000000000000000000000000000000000001000000,64
7     0000000000000000000000000000000000000000000000000000000010000000,128
8     0000000000000000000000000000000000000000000000000000000100000000,256
9     0000000000000000000000000000000000000000000000000000001000000000,512
10     0000000000000000000000000000000000000000000000000000010000000000,1024
11     0000000000000000000000000000000000000000000000000000100000000000,2048
12     0000000000000000000000000000000000000000000000000001000000000000,4096
13     0000000000000000000000000000000000000000000000000010000000000000,8192
14     0000000000000000000000000000000000000000000000000100000000000000,16384
15     0000000000000000000000000000000000000000000000001000000000000000,32768
16     0000000000000000000000000000000000000000000000010000000000000000,65536
17     0000000000000000000000000000000000000000000000100000000000000000,131072
18     0000000000000000000000000000000000000000000001000000000000000000,262144
19     0000000000000000000000000000000000000000000010000000000000000000,524288
20     0000000000000000000000000000000000000000000100000000000000000000,1048576
21     0000000000000000000000000000000000000000001000000000000000000000,2097152
22     0000000000000000000000000000000000000000010000000000000000000000,4194304
23     0000000000000000000000000000000000000000100000000000000000000000,8388608
24     0000000000000000000000000000000000000001000000000000000000000000,16777216
25     0000000000000000000000000000000000000010000000000000000000000000,33554432
26     0000000000000000000000000000000000000100000000000000000000000000,67108864
27     0000000000000000000000000000000000001000000000000000000000000000,134217728
28     0000000000000000000000000000000000010000000000000000000000000000,268435456
29     0000000000000000000000000000000000100000000000000000000000000000,536870912
30     0000000000000000000000000000000001000000000000000000000000000000,1073741824
31     0000000000000000000000000000000010000000000000000000000000000000,2147483648
32     0000000000000000000000000000000100000000000000000000000000000000,4294967296
33     0000000000000000000000000000001000000000000000000000000000000000,8589934592
34     0000000000000000000000000000010000000000000000000000000000000000,17179869184
35     0000000000000000000000000000100000000000000000000000000000000000,34359738368
36     0000000000000000000000000001000000000000000000000000000000000000,68719476736
37     0000000000000000000000000010000000000000000000000000000000000000,137438953472
38     0000000000000000000000000100000000000000000000000000000000000000,274877906944
39     0000000000000000000000001000000000000000000000000000000000000000,549755813888
40     0000000000000000000000010000000000000000000000000000000000000000,1099511627776
41     0000000000000000000000100000000000000000000000000000000000000000,2199023255552
42     0000000000000000000001000000000000000000000000000000000000000000,4398046511104
43     0000000000000000000010000000000000000000000000000000000000000000,8796093022208
44     0000000000000000000100000000000000000000000000000000000000000000,17592186044416
45     0000000000000000001000000000000000000000000000000000000000000000,35184372088832
46     0000000000000000010000000000000000000000000000000000000000000000,70368744177664
47     0000000000000000100000000000000000000000000000000000000000000000,140737488355328
48     0000000000000001000000000000000000000000000000000000000000000000,281474976710656
49     0000000000000010000000000000000000000000000000000000000000000000,562949953421312
50     0000000000000100000000000000000000000000000000000000000000000000,1125899906842624
51     0000000000001000000000000000000000000000000000000000000000000000,2251799813685248
52     0000000000010000000000000000000000000000000000000000000000000000,4503599627370496
53     0000000000100000000000000000000000000000000000000000000000000000,9007199254740992
54     0000000001000000000000000000000000000000000000000000000000000000,18014398509481984
55     0000000010000000000000000000000000000000000000000000000000000000,36028797018963968
56     0000000100000000000000000000000000000000000000000000000000000000,72057594037927936
57     0000001000000000000000000000000000000000000000000000000000000000,144115188075855872
58     0000010000000000000000000000000000000000000000000000000000000000,288230376151711744
59     0000100000000000000000000000000000000000000000000000000000000000,576460752303423488
60     0001000000000000000000000000000000000000000000000000000000000000,1152921504606846976
61     0010000000000000000000000000000000000000000000000000000000000000,2305843009213693952
62     0100000000000000000000000000000000000000000000000000000000000000,4611686018427387904
63     1000000000000000000000000000000000000000000000000000000000000000,9223372036854775808
       1111111111111111111111111111111111111111111111111111111111111111,18446744073709551615