leetcode4:Permutation

#include <utility>
#include <iostream>
#include <vector>
#include <algorithm>
//the next permutation
template<class BidirIt>
bool STL_next_permutation(BidirIt first, BidirIt last)
{
    if (first == last) return false;
    BidirIt i = last;
    if (first == --i) return false;
 
    while (1) {
        BidirIt i1, i2;
 
        i1 = i;
        --i;
        if (*i < *i1) {
            i2 = last;
            while (!(*i < *--i2))
                ;
            std::iter_swap(i, i2);
            std::reverse(i1, last);
            return true;
        }
        if (i == first) {
            std::reverse(first, last);
            return false;
        }
    }
}
void nextPermutation(int A[],int len)
{
    STL_next_permutation(A, A+len);
}


//full pemutation
void fullPerm(int A[],int m,int n)
{
    if(m == n)
    {
        for(int i=0;i<n+1;i++)
            std::cout << A[i] << " ";
        std::cout << std::endl;
        return;
    }
    else
    {
        for(int i=m;i<n+1;i++)
        {
            std::swap(A[m], A[i]);
            fullPerm(A,m+1,n);
            std::swap(A[m], A[i]);
        }
    }
}


int Factorial(int n)
{
    int fac=1;
    for(int i=1;i<=n;i++)
    {
        fac *=i;
    }
    return fac;
}
//康托编码第k个序列
void CantorCode(int A[],int len,int k)
{
    --k;
    std::vector<std::pair<int,bool>> v;
    for(int i=0;i<len;i++)
    {
        v.emplace_back(A[i],false);
    }

    for(int i=0;i<len;i++)
    {
        int j;
        int t=k/Factorial(len-i-1);
        for(j=0;j<len;j++)
        {
            if(!v[j].second)
            {
                if(t==0) break;
                --t;    
            }    
        }
        A[i]=v[j].first;
        v[j].second=true;
        k=k%Factorial(len-i-1);
    }
}