【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;
}