生成组合序列算法

来源：互联网发布：淘宝新店旺旺号采集编辑：程序博客网时间：2024/05/29 14:14

生成组合序列

1.递归算法

生成C(5,3)

#include <iostream>#include <vector>using namespace std;vector<vector<int>> s;vector<int> source;void getCombination(int elementNeed, int startPos, const vector<int> &oneResult){    if(elementNeed == 0)    {        s.push_back(oneResult);        return;    }    while(startPos < source.size())    {        vector<int> tmp = oneResult;        tmp.push_back(source[startPos]);        getCombination(elementNeed - 1, startPos + 1, tmp);        ++startPos;    }}int main(int argc, const char * argv[]){    source = {1, 2, 3, 4, 5};    vector<int> tmp;    getCombination(3, 0, tmp);    for(auto k : s)    {        for(auto i : k)        {            cout << i << ' ';        }        cout << endl;    }    return 0;}

2.非递归版本

生成C(5,3)

#include <iostream>#include <vector>using namespace std;vector<vector<int>> s;void getCombination(const vector<int> &source, int elementNeed){    if(elementNeed == 0)    {        return;    }    if(elementNeed > source.size())    {        return;    }    vector<int> pos;    vector<int> tmp;    for(int i = 0; i < elementNeed; ++i)    {        pos.push_back(i);        tmp.push_back(source[i]);    }    while(pos[0] + elementNeed <= source.size())    {        for(int i = 0; i < pos.size(); ++i)        {            tmp[i] = source[pos[i]];        }        s.push_back(tmp);        int k = pos.size() - 1;        while(k>0 && pos[k] + elementNeed - k == source.size()) --k;        ++pos[k];        ++k;        while(k < pos.size())        {            pos[k] = pos[k - 1] + 1;            ++k;        }    }}int main(int argc, const char * argv[]){    vector<int> source = {1, 2, 3, 4, 5};    getCombination(source, 3);    for(auto k : s)    {        for(auto i : k)        {            cout << i << ' ';        }        cout << endl;    }    return 0;}

3.优化的非递归版本

生成C(5,3)，优化减少了赋值的次数

#include <iostream>#include <vector>using namespace std;vector<vector<int>> s;void getCombination(const vector<int> &source, int elementNeed){    if(elementNeed == 0)    {        return;    }    if(elementNeed > source.size())    {        return;    }    vector<int> pos;    vector<int> tmp;    for(int i = 0; i<elementNeed; ++i)    {        pos.push_back(i);        tmp.push_back(source[i]);    }    while(pos[0] + elementNeed <= source.size())    {        s.push_back(tmp);        int k = pos.size() - 1;        while(k>0 && pos[k] + elementNeed - k == source.size())        {            --k;        }        ++pos[k];        tmp[k] = source[pos[k]];        ++k;        while(k < pos.size())        {            pos[k] = pos[k - 1] + 1;            if(pos[k] < source.size())            {                tmp[k] = source[pos[k]];            }            ++k;        }    }}int main(int argc, const char * argv[]){    vector<int> source = {1, 2, 3, 4, 5};    getCombination(source, 3);    for(auto k : s)    {        for(auto i : k)        {            cout << i << ' ';        }        cout << endl;    }    return 0;}

阅读全文

0 0