【C/C++】OJ笔试常用的函数

unique函数
删除连续重复的范围

template <class ForwardIterator>  ForwardIterator unique ( ForwardIterator first, ForwardIterator last );template <class ForwardIterator, class BinaryPredicate>  ForwardIterator unique ( ForwardIterator first, ForwardIterator last, BinaryPredicate pred );

返回值，返回的是迭代器，指向新的末端
测试

// unique algorithm example#include <iostream>#include <algorithm>#include <vector>using namespace std;bool myfunction (int i, int j) {  return (i==j);}int main () {  int myints[] = {10,20,20,20,30,30,20,20,10};    // 10 20 20 20 30 30 20 20 10  vector<int> myvector (myints,myints+9);  vector<int>::iterator it;  // using default comparison:  it = unique (myvector.begin(), myvector.end()); // 10 20 30 20 10 ?  ?  ?  ?                                                  //                ^  myvector.resize( it - myvector.begin() );       // 10 20 30 20 10  // using predicate comparison:  unique (myvector.begin(), myvector.end(), myfunction);   // (no changes)  // print out content:  cout << "myvector contains:";  for (it=myvector.begin(); it!=myvector.end(); ++it)    cout << " " << *it;  cout << endl;  return 0;}

sort函数
注：参数必须是RandomAccessIterator类型的迭代器，即：只有vector，string，array，deque类型，可以用sort。

参数：区间是左闭右开的。默认是从小到大排序

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

测试

// sort algorithm example#include <iostream>#include <algorithm>#include <vector>using namespace std;bool myfunction (int i,int j) { return (i<j); }struct myclass {  bool operator() (int i,int j) { return (i<j);}} myobject;int main () {  int myints[] = {32,71,12,45,26,80,53,33};  vector<int> myvector (myints, myints+8);               // 32 71 12 45 26 80 53 33  vector<int>::iterator it;  // using default comparison (operator <):  sort (myvector.begin(), myvector.begin()+4);           //(12 32 45 71)26 80 53 33  // using function as comp  sort (myvector.begin()+4, myvector.end(), myfunction); // 12 32 45 71(26 33 53 80)  // using object as comp  sort (myvector.begin(), myvector.end(), myobject);     //(12 26 32 33 45 53 71 80)  // print out content:  cout << "myvector contains:";  for (it=myvector.begin(); it!=myvector.end(); ++it)    cout << " " << *it;  cout << endl;  //myvector contains: 12 26 32 33 45 53 71 80  return 0;}

reverse函数

翻转函数，将[first,last)范围的元素，进行翻转。
Reverse range
Reverses the order of the elements in the range [first,last).

template <class BidirectionalIterator>  void reverse ( BidirectionalIterator first, BidirectionalIterator last);

测试代码

vector<int> myvector;  // 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

lower_bound函数和upper_bound 函数

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 );

lower_bound函数 返回一个迭代器，指向范围内[first,end)的不小于value的值。

upper_bound 函数 返回一个迭代器，指向范围内[first,end)的大于value的值。

测试代码

// lower_bound/upper_bound example#include <iostream>#include <algorithm>#include <vector>using namespace std;int main () {  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); //                   ^  return 0;}