[小算法]从M个不同字符中任取N个字符的所有组合

非递归算法

 

#include "stdafx.h"
#include <iostream>

using namespace std;

void GetCombination(char * chars, int n);

int main()
{
    GetCombination("abcdefg", 3);
    system("pause");
    return 0;
}

void GetCombination(char * chars, int n)
{
    int index[10];
    int strLength = strlen(chars);
    for (int i = 0; i < n;i++)
    {
        index[i] = i;
    }
    bool end = false;
    while(!end)
    {
        for(int i = 0; i < n; i++)
        {
            cout << chars[index[i]];
        }
        cout << endl;
        for(int i = n - 1; i >= -1; i--)
        {
            if(i < 0)
            {
                end = true;
                break;
            }
            if(index[i] < strLength - n + i)//strLength - 1 - ( n - 1 -i)
            {
                index[i]++;
                for(int j = i + 1; j < n ;j++)
                {
                    index[j] = index[j - 1] + 1;
                }
                break;
            }
        }
    }
}