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);
}
}