Reorganize the trivial knowledge points at the end of the term

1. insert Is for map
2. push_back Is for vector
3. Use insert when , And use make_pair(,)
4. If used pair, Then the data type should be indicated , If used make_pair Do not specify the data type .
5. Read file operation ,while() Put... In brackets fstream Later
6. Note in file operation ,>> It is a file reading operation ,<< It is a file writing operation , Don't get confused .（ Memory method can be understood in this way ：cin>>....        cout<<....        cin It's input ,cout It's output .

         The first way of understanding ：

                 Output to file , Therefore, the written document corresponds to cout<<

         The second way of understanding ：

                 and cin cout Just the opposite

        ）

     7.find lookup （ Is limited to map Container can use this function ）

     8.map and multimap Special search function of

operation	effect
count(key)	return ” Key value is equal to key” Number of elements of
find(key)	return ” Key value is equal to key” The first element of , No return found end
lower_bound(key)	return ” Key value is greater than or equal to key” The first element of
upper_bound(key)	return ” The key value is greater than key” The first element of
equal_range(key)	return ” Key value is equal to key” Element interval of

especially lower_bound and upper_bound function , In the past, I paid less attention , This exam is inevitable .

     9. Consider using set Containers , Take advantage of its automatic weight removal feature .（ Don't forget to add #include<set> The header file ）

     10.

lower_bound	requirement [first,last) Is ordered , check Find greater than or equal to val The most Small bit Set up
upper_bound	requirement [first,last) Is ordered , check Find more than val The minimum position of

     11.vector About function sorting

operation	effect
c.pop_back()	Remove the last element but do not return the last element
c.erase(pos)	Delete pos The element of location , Returns the position of the next element
c.erase(beg,end)	Delete range [beg,end] All elements in , Returns the position of the next element
c.clear()	Remove all elements , Empty the container
c.resize(num)	Change the number of elements to num（ Add elements with defalut Constructors produce , Redundant elements are deleted ）
c.resize(num,e)	Change the number of elements to num（ The added element is e Copy of ）
c.insert(pos,e)	stay pos Position insert element e Copy of , And return the location of the new element
c.insert(pos,n,e)	stay pos Position insert n Elements e Copy of
c.insert(pos,beg,end)	stay pos Position insert interval [beg,end] Copies of all elements in the
c.push_back(e)	Add an element at the end e Copy of

#include<bits/stdc++.h>
using namespace std;
int main()
{
vector<int> s;
s.push_back(5);
s.push_back(45);
s.push_back(12);
s.push_back(8);
vector<int>::iterator f=s.begin();
	s.insert(f,5,12);
for(f=s.begin();f!=s.end();f++)
	{
cout<<*f<<" ";	
	}	

return 0;
 } 

The above figure shows the use of iterators for insert The use of functions that insert multiple elements consecutively .