algorithm vector resverse函数

Reverse range

Reverses the order of the elements in the range [first,last).

The behavior of this function template is equivalent to:

template <class BidirectionalIterator>
  void reverse ( BidirectionalIterator first, BidirectionalIterator last)
{
  while ((first!=last)&&(first!=--last))
    swap (*first++,*last);
}

Parameters

first, last

Bidirectional iterators to the initial and final positions of the sequence to be reversed. The range used is [first,last), which contains all the elements between firstand last, including the element pointed by first but not the element pointed by last.

Example

// reverse algorithm example
#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;

int main () {
  vector<int> myvector;
  vector<int>::iterator it;

  // set some values:
  for (int i=1; i<10; ++i) myvector.push_back(i); // 1 2 3 4 5 6 7 8 9

  reverse(myvector.begin(),myvector.end());       // 9 8 7 6 5 4 3 2 1

  // print out content:
  cout << "myvector contains:";
  for (it=myvector.begin(); it!=myvector.end(); ++it)
    cout << " " << *it;

  cout << endl;

  return 0;
}

Output:

myvector contains: 9 8 7 6 5 4 3 2 1

Complexity

Linear: Calls swap one half the length of range [first,last) times.