生成汉明距离t内的所有位序列

问题描述：

给出一个位向量v，计算汉明距离为1且v， then 的距离为2的位的集合，直到输入参数t.

Given a vector of bits v, compute the collection of bits that have Hamming distance 1 with v, then with distance 2, up to an input parameter t.

所以

011  I should get
~~~ 
111
001
010
~~~ -> 3 choose 1 in number
101
000
110
~~~ -> 3 choose 2
100
~~~ -> 3 choose 3

如何有效计算?向量并不总是尺寸为3，例如可能是6.这将在我的真实代码中运行很多次，因此也将提高效率(甚至通过支付更多的内存).

How to efficiently compute this? The vector won't be always of dimension 3, e.g. it could be 6. This will run numerous time in my real code, so some efficiency would be welcome as well (even by paying more memory).

我的尝试:

#include <iostream>
#include <vector>

void print(const std::vector<char>& v, const int idx, const char new_bit)
{
    for(size_t i = 0; i < v.size(); ++i)
        if(i != idx)
            std::cout << (int)v[i] << " ";
        else
            std::cout << (int)new_bit << " ";
    std::cout << std::endl;
}

void find_near_hamming_dist(const std::vector<char>& v, const int t)
{
    // if t == 1
    for(size_t i = 0; i < v.size(); ++i)
    {
        print(v, i, v[i] ^ 1);
    }

    // I would like to produce t == 2
    // only after ALL the t == 1 results are reported
    /* how to? */
}

int main()
{
    std::vector<char> v = {0, 1, 1};
    find_near_hamming_dist(v, 1);
    return 0; 
}

输出:

MacBook-Pro:hammingDist gsamaras$ g++ -Wall -std=c++0x hammingDist.cpp -o ham
MacBook-Pro:hammingDist gsamaras$ ./ham
1 1 1 
0 0 1 
0 1 0

答

#include <stdio.h>
#include <stdint.h>
#include <string.h>

void magic(char* str, int i, int changesLeft) {
        if (changesLeft == 0) {
                printf("%s\n", str);
                return;
        }
        if (i < 0) return;
        // flip current bit
        str[i] = str[i] == '0' ? '1' : '0';
        magic(str, i-1, changesLeft-1);
        // or don't flip it (flip it again to undo)
        str[i] = str[i] == '0' ? '1' : '0';
        magic(str, i-1, changesLeft);
}

int main(void) {
        char str[] = "011";
        printf("%s\n", str);
        size_t len = strlen(str);
        size_t maxDistance = len;
        for (size_t i = 1 ; i <= maxDistance ; ++i) {
                printf("Computing for distance %d\n", i);
                magic(str, len-1, i);
                printf("----------------\n");
        }
        return 0;
}

输出:

MacBook-Pro:hammingDist gsamaras$ nano kastrinis.cpp
MacBook-Pro:hammingDist gsamaras$ g++ -Wall kastrinis.cpp 
MacBook-Pro:hammingDist gsamaras$ ./a.out 
011
Computing for distance 1
010
001
111
----------------
Computing for distance 2
000
110
101
----------------
Computing for distance 3
100
----------------

生成汉明距离t内的所有位序列

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