Next Permutation--leetcode

Mplement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers.

If Such arrangement is not a possible, it must rearrange it as the lowest possible order (ie, sorted in ascending order).

The replacement must is in-place, do not allocate extra memory.

Here is some examples. Inputs is in the left-hand column and its corresponding outputs is in the right-hand column.
1,2,3→ 1,3,2
3,2,1→ 1,2,3

1,1,5→1,5,1

Using the idea of STL, from the next to find a pair of adjacent number, in a pair of adjacent number of the first element is less than the second element, remember to do *i<*ii, from the back to find the first element *j, yes *j>*i, then Exchange *i and *j, and then Exchange from *II start (contains * ii) to the sequence at the end of the array.

void Rserve (vector<int>& vec,int begin,int end)  {while      (begin <= End)      {          swap (Vec[begin] , Vec[end]);          begin++;          end--;      }  }     BOOL Findpair (vector<int>& vec,int& first,int& second)  {      int last = Vec.size ()-1;      for (; last>0;last--)      {          second = last;          first = last-1;          if (Vec[first] < Vec[second])              return true;      return false;  }    void Nextpermutation (vector<int>& vec)  {      int first,second,index;      if (Findpair (Vec,first,second))      {          index = vec.size ()-1;          for (; index>=first;index--)          {              if (Vec[index] > Vec[first]) break                  ;          }          Swap (Vec[index],vec[first]);          Rserve (Vec,second,vec.size ()-1);       }  

Next Permutation--leetcode