python/C++专题课程/全排列/AllPermutation.cpp

#include <iostream>
#include <cstring>

//全排列代码说明   

// https://www.jianshu.com/p/e0de4c9b73f2?utm_campaign=maleskine&utm_content=note&utm_medium=seo_notes&utm_source=recommendation

using namespace std;

//在[from, to]区间中是否有字符与下标为from的字符相等  
bool IsSwap(char* from, char* to)
{
    char* p;
    for(p = from; p < to; p++)
    {
        if(*p == *to)
            return false;   
    }   
    return true;
} 

void AllPermutation(char* perm, int from, int to)
{
    if(from > to)
        return;
            
    if(from == to)     //打印当前排列 
    {
        static int count = 1;    //局部静态变量，用来统计全排列的个数  
        cout << count++ << ":" << perm;
        cout << endl;
    }
    if(from < to)     //用递归实现全排列 
    {
        for(int j = from; j <= to; j++)    //第j个字符分别与它后面的字符交换就能得到新的排列
        {
            if(IsSwap((perm + j), (perm + to)))
            {
                swap(perm[j], perm[from]);
                //cout<<0;
                AllPermutation(perm, from + 1, to);
                //cout<<1;
                swap(perm[j], perm[from]);
                //cout<<2;
            }
        }
    }
}

int main()
{
    char str[100];
    cin >> str;
    AllPermutation(str, 0, strlen(str) - 1);
    return 0;
}