在C ++ STL中设置lower_bound()函数
在C++STL中设置lower_bound()函数将返回一个迭代器，该迭代器指向容器中的元素，该元素等效于在参数中传递的k。如果set容器中不存在k，则该函数返回一个迭代器，该迭代器指向刚好大于k的紧邻的下一个元素。
算法
Begin Initialize an empty set container s. Initializing a set container as inetrator. Insert some elements in s set container. Call function to find the lower bound value of a given key, which is passed to iter set container. Print the lower bound value of the given key. End.
范例程式码
#include<iostream>
#include <bits/stdc++.h>
using namespace std;
int main(){
set<int> s; //Declaring an empty set container
set<int>::iterator iter; //Declaring a set container as iterator which will point to the lower bound value
s.insert(7); //inserting elements in the set container s
s.insert(6);
s.insert(1);
s.insert(4);
s.insert(2);
s.insert(9);
s.insert(10);
iter = s.lower_bound(4); //passing a key by parameter to find its lower bound
cout <<"The lower bound of 4 is: "<< *iter << " "<<endl; //printing the lowerbound value
iter = s.lower_bound(5);
cout <<"The lower bound of 5 is: " <<*iter << " "<<endl;
iter = s.lower_bound(30);
cout <<"The lower bound of 30 is: " <<*iter << " "<<endl;
return 0;
}输出结果
The lower bound of 4 is: 4 The lower bound of 5 is: 6 The lower bound of 30 is: 7