c++常用摘抄（一）
1.标准初始化函数
std::fill(首地址，尾地址，value) || 用于在首尾地址之间填充value值，对应matlab的ones(1:n)函数
1 template <class ForwardIterator, class T> 2 void fill (ForwardIterator first, ForwardIterator last, const T& val) 3 { 4 while (first != last) { 5 *first = val; 6 ++first; 7 } 8 }
1 // fill algorithm example 2 #include <iostream> // std::cout 3 #include <algorithm> // std::fill 4 #include <vector> // std::vector 5 6 int main () { 7 std::vector<int> myvector (8); // myvector: 0 0 0 0 0 0 0 0 8 9 std::fill (myvector.begin(),myvector.begin()+4,5); // myvector: 5 5 5 5 0 0 0 0 10 std::fill (myvector.begin()+3,myvector.end()-2,8); // myvector: 5 5 5 8 8 8 0 0 11 12 std::cout << "myvector contains:"; 13 for (std::vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it) 14 std::cout << ' ' << *it; 15 std::cout << '\n'; 16 17 return 0; 18 }
myvector contains: 5 5 5 8 8 8 0 0
2.交换函数
std::swap(value1,value2)
1 template <class T> void swap ( T& a, T& b ) 2 { 3 T c(a); a=b; b=c; 4 }
1 // swap algorithm example (C++11) 2 #include <iostream> // std::cout 3 #include <utility> // std::swap 4 5 int main () { 6 7 int x=10, y=20; // x:10 y:20 8 std::swap(x,y); // x:20 y:10 9 10 int foo[4]; // foo: ? ? ? ? 11 int bar[] = {10,20,30,40}; // foo: ? ? ? ? bar: 10 20 30 40 12 std::swap(foo,bar); // foo: 10 20 30 40 bar: ? ? ? ? 13 14 std::cout << "foo contains:"; 15 for (int i: foo) std::cout << ' ' << i; 16 std::cout << '\n'; 17 18 return 0; 19 }
foo contains: 10 20 30 40
3.在list 双端链表中的迭代器函数
std::advance(iterator pos,distance n) 注意：n可以取正或负整数值
1 // advance example 2 #include <iostream> // std::cout 3 #include <iterator> // std::advance 4 #include <list> // std::list 5 6 int main () { 7 std::list<int> mylist; 8 for (int i=0; i<10; i++) mylist.push_back (i*10); 9 10 std::list<int>::iterator it = mylist.begin(); 11 12 std::advance (it,5); 13 14 std::cout << "The sixth element in mylist is: " << *it << '\n'; 15 16 std::advance (it,-4); 17 18 std::cout << "now let it back_forward: " << *it << '\n'; 19 system("PAUSE"); 20 return 1; 21 } 22
4.std::list::rease和std::list::remove的区别
erase：
Removes from the list container either a single element (position) or a range of elements ([first,last)).
format:
1 iterator erase (iterator position); 2 iterator erase (iterator first, iterator last);//注意：删除的是[first,last)前开后闭区间
1 // erasing from list 2 #include <iostream> 3 #include <list> 4 5 int main () 6 { 7 std::list<int> mylist; 8 std::list<int>::iterator it1,it2; 9 10 // set some values: 11 for (int i=1; i<10; ++i) mylist.push_back(i*10); 12 13 // 10 20 30 40 50 60 70 80 90 14 it1 = it2 = mylist.begin(); // ^^ 15 advance (it2,6); // ^ ^ 16 ++it1; // ^ ^ 17 18 it1 = mylist.erase (it1); // 10 30 40 50 60 70 80 90 19 // ^ ^ 20 21 it2 = mylist.erase (it2); // 10 30 40 50 60 80 90 22 // ^ ^ 23 24 ++it1; // ^ ^ 25 --it2; // ^ ^ 26 27 mylist.erase (it1,it2); // 10 30 60 80 90 28 // ^ 29 30 std::cout << "mylist contains:"; 31 for (it1=mylist.begin(); it1!=mylist.end(); ++it1) 32 std::cout << ' ' << *it1; 33 std::cout << '\n'; 34 35 return 0; 36 }
remove：
Removes from the container all the elements that compare equal to val.
Removes from the container all the elements that compare equal to val.
format：
1 void remove (const value_type& val);
1 // remove from list 2 #include <iostream> 3 #include <list> 4 5 int main () 6 { 7 int myints[]= {17,89,7,14}; 8 std::list<int> mylist (myints,myints+4);//good skill：用数组初始化list 9 10 mylist.remove(89); 11 12 std::cout << "mylist contains:"; 13 for (std::list<int>::iterator it=mylist.begin(); it!=mylist.end(); ++it) 14 std::cout << ' ' << *it; 15 std::cout << '\n'; 16 17 return 0; 18 }
output:
mylist contains: 17 7 14
5.list的初始化构造方法
1 // constructing lists 2 #include <iostream> 3 #include <list> 4 5 int main () 6 { 7 // constructors used in the same order as described above: 8 std::list<int> first; // empty list of ints 9 std::list<int> second (4,100); // four ints with value 100 10 std::list<int> third (second.begin(),second.end()); // iterating through second//注意地址的前闭后开 11 std::list<int> fourth (third); // a copy of third 12 13 // the iterator constructor can also be used to construct from arrays: 14 int myints[] = {16,2,77,29}; 15 std::list<int> fifth (myints, myints + sizeof(myints) / sizeof(int) );//注意地址的前闭后开
16 17 std::cout << "The contents of fifth are: "; 18 for (std::list<int>::iterator it = fifth.begin(); it != fifth.end(); it++) 19 std::cout << *it << ' '; 20 21 std::cout << '\n'; 22 23 return 0; 24 }
