生成全排列示例

来源：互联网发布：unity3d 镜面反射编辑：程序博客网时间：2024/05/16 15:08

代码示例

#include <iostream>#include <string>using namespace std;void fun1(string & list,int n , int index){    if (index >= n)    {        cout << list << endl;    }    else    {        for (int i = index; i < n; i++)        {            swap(list[i] , list[index]);            fun1(list , n , index + 1);            swap(list[i] , list[index]);        }    }}void fun2(string & list , int n){    if (n == 1)    {        cout << list << endl;    }    else    {        for (int i = 1; i <= n; i++)        {            fun2(list , n - 1);            if (n % 2 == 1)            {                swap(list[0] , list[n - 1]);            }            else            {                swap(list[i - 1] , list[n - 1]);            }        }    }}void fun3(string & str){       int left = 0;    int right = 0;    for (int i = str.length() - 1; i > 0; i--)    {        if(str[i - 1] < str[i])         {            left = i - 1;            break;        }        if(i == 1)               return;    }    for (i = str.length() - 1; i > left; i--)    {        if(str[i] > str[left])        {            swap(str[left] , str[i]);            break;        }    }    left++;    right = str.length() - 1;    while(left < right)    {        swap(str[left++] , str[right--]);    }}int factorial(int n){    return n == 1 ? n : n * factorial(n - 1);}int main(){    //string list("123456");    //fun1(list.length() , 0);    //fun2(list.length());    string str("123456");    cout << str << endl;        for (int i = 1; i < factorial(str.length()); i++)    {        fun3(str); //按照字典序生成下一个排列        cout << str << endl;    }    return 0;}

1.找到使得ai<ai+1的最大i //ai+1>ai+2>...>an
2.找到使得ai<aj的最大索引j //j>=i+1
3.交换ai和aj //ai+1ai+2...an仍保持降序
4.将ai+1到an的元素反序

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