整理下STL algorithms（3）

sort（排序）：

template <class RandomAccessIterator>
  void sort ( RandomAccessIterator first, RandomAccessIterator last );

template <class RandomAccessIterator, class Compare>
  void sort ( RandomAccessIterator first, RandomAccessIterator last, Compare comp );
该方法用于排序，comp用于指定元素比较的函数

类似的有stable_sort（保持比较相等元素的原顺序）

partial_sort（部分排序）：
template <class RandomAccessIterator>
  void partial_sort ( RandomAccessIterator first, RandomAccessIterator middle,
                      RandomAccessIterator last );

template <class RandomAccessIterator, class Compare>
  void partial_sort ( RandomAccessIterator first, RandomAccessIterator middle,
                      RandomAccessIterator last, Compare comp );
对序列进行部分排序，对first和middle之间的元素进行排序～～其余的不管

partial_sort_copy是该算法的copy版本：

template <class InputIterator, class RandomAccessIterator>
  RandomAccessIterator
    partial_sort_copy ( InputIterator first,InputIterator last,
                        RandomAccessIterator result_first,
                        RandomAccessIterator result_last );

template <class InputIterator, class RandomAccessIterator, class Compare>
  RandomAccessIterator
    partial_sort_copy ( InputIterator first,InputIterator last,
                        RandomAccessIterator result_first,
                        RandomAccessIterator result_last, Compare comp );
nth_element:
template <class RandomAccessIterator>
  void nth_element ( RandomAccessIterator first, RandomAccessIterator nth,
                     RandomAccessIterator last );

template <class RandomAccessIterator, class Compare>
  void nth_element ( RandomAccessIterator first, RandomAccessIterator nth,
                     RandomAccessIterator last, Compare comp );
将第n个元素放在第n个位置


  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

  random_shuffle (myvector.begin(), myvector.end());

  // using default comparison (operator <):
  nth_element (myvector.begin(), myvector.begin()+5, myvector.end());

结果为：

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

关于二分查找的操作：
lower_bound:

template <class ForwardIterator, class T>
  ForwardIterator lower_bound ( ForwardIterator first, ForwardIterator last,
                                const T& value );

template <class ForwardIterator, class T, class Compare>
  ForwardIterator lower_bound ( ForwardIterator first, ForwardIterator last,
                                const T& value, Compare comp );
该方法会找到序列中可以存放value的值的迭代器部分。与之相对应的方法是upper_bound方法可以如下使用：


  int myints[] = {10,20,30,30,20,10,10,20};
  vector<int> v(myints,myints+8);           // 10 20 30 30 20 10 10 20
  vector<int>::iterator low,up;

  sort (v.begin(), v.end());                // 10 10 10 20 20 20 30 30

  low=lower_bound (v.begin(), v.end(), 20); //          ^
  up= upper_bound (v.begin(), v.end(), 20); //  

结果为：
lower_bound at position 3
upper_bound at position 6


equal_range:

template <class ForwardIterator, class T>
  pair<ForwardIterator,ForwardIterator>
    equal_range ( ForwardIterator first, ForwardIterator last, const T& value );

template <class ForwardIterator, class T, class Compare>
  pair<ForwardIterator,ForwardIterator>
    equal_range ( ForwardIterator first, ForwardIterator last, const T& value,
                  Compare comp );
返回的是一个pair.
pair.first是value的起始位置，pair.second是结束位置（不包括在内～）

binary_search（二分查找）：
template <class ForwardIterator, class T>
  bool binary_search ( ForwardIterator first, ForwardIterator last,
                       const T& value );

template <class ForwardIterator, class T, class Compare>
  bool binary_search ( ForwardIterator first, ForwardIterator last,
                       const T& value, Compare comp );

测试有序序列中是否包含要查找的元素。