C++STL common operations prev, next articles
Introduction:
1.prev: reverse
2.next: displacement
We first create a set container, and put 10 numbers from 1 to 10 in the container
set<int> s;
for(int i = 1;i <= 10;++i)
s.insert(i);
At this time, the elements in the container s are 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
prev：
If the lower_bound function is used
cout<<*s.lower_bound(5)<<"\n";
Should output the first number greater than or equal to 5, here should be output 5
So what do we use prev?
cout<<*prev(s.lower_bound(5))<<"\n";
The output here is 4, which means that the initial greater than or equal becomes less than, which has a reverse effect.
next：
auto it = s.begin();
cout<<*next(it,2);
The output here is 3, which is the number in the last two positions of s.begin().
What if the parameter is negative?
it = --s.end();
cout<<*next(it,-3);
The output is the number of the first three positions, which is 7.
#include<iostream>
#include<set>
using namespace std;
int main(){
set<int> s;
for(int i = 1;i <= 10;++i)
s.insert(i);
cout<<*s.lower_bound(5)<<"\n";
cout<<*prev(s.lower_bound(5))<<"\n";
auto it = s.begin();
cout<<*next(it,2)<<"\n";
it = --s.end();
cout<<*next(it,-3);
return 0;
}
There are many more content of prev and next, here is a brief introduction
If you find any problems, please correct me!
Please leave a message if you don’t understand!