CPP

lower_bound in C++

// CPP program to illustrate
// std :: lower_bound
#include <bits/stdc++.h>
 
// Driver code
int main()
{
    // Input vector
    std::vector<int> v{ 10, 20, 30, 30, 30, 40, 50 };
 
    // Print vector
    std::cout << "Vector contains :";
    for (unsigned int i = 0; i < v.size(); i++)
        std::cout << " " << v[i];
    std::cout << "
";
 
    std::vector<int>::iterator low1, low2, low3;
     
    // std :: lower_bound
    low1 = std::lower_bound(v.begin(), v.end(), 30);
    low2 = std::lower_bound(v.begin(), v.end(), 35);
    low3 = std::lower_bound(v.begin(), v.end(), 55);
 
    // Printing the lower bounds
    std::cout
        << "
lower_bound for element 30 at position : "
        << (low1 - v.begin());
    std::cout
        << "
lower_bound for element 35 at position : "
        << (low2 - v.begin());
    std::cout
        << "
lower_bound for element 55 at position : "
        << (low3 - v.begin());
 
    return 0;
}

upper bound c++

upper_bound(v.begin(), v.end(), val);
Returns an iterator pointing to the first element in the range [first,last) which compares greater than val.

lower and upper bound c++

Iterator lower_bound (Iterator first, Iterator last, const val) 
lower_bound returns an iterator pointing to the first element in the range [first,last) which has a value not less than ‘val’. 

Iterator upper_bound (Iterator first, Iterator last, const val) 
upper_bound returns an iterator pointing to the first element in the range [first,last) which has a value greater than ‘val’.         
                                                                            
If the value is not present in the vector then it returns the end iterator.

lower bound and upper bound in c++

#include<bits/stdc++.h>
using namespace std;

int main(){
    int n;cin>>n;
    vector<int>v;

    for(int i=0;i<n;i++){
        cin>>v[i];
    }
    sort(v.begin(),v.end());


    //lower bound for vector
    auto pointer1 = lower_bound(v.begin(), v.end(), 7);
    cout<<(*pointer1)<<endl;

    //lower bound for array;
    int array[n];
    for(int i=0;i<n;i++){
        cin>>array[i];
    }
    sort(array,array+n);
    //lowerbound
    int *pointer2 = lower_bound(array, array+n, 7);

    //if you want upper bound then just replace lower_bound with upper_bound
}

finding lower bound and upper bound in vector c++

// lower_bound/upper_bound example
#include <iostream>     // std::cout
#include <algorithm>    // std::lower_bound, std::upper_bound, std::sort
#include <vector>       // std::vector

int main () {
  int myints[] = {10,20,30,30,20,10,10,20};
  std::vector<int> v(myints,myints+8);           // 10 20 30 30 20 10 10 20

  std::sort (v.begin(), v.end());                // 10 10 10 20 20 20 30 30

  std::vector<int>::iterator low,up;
  low=std::lower_bound (v.begin(), v.end(), 20); //          ^
  up= std::upper_bound (v.begin(), v.end(), 20); //                   ^

  std::cout << "lower_bound at position " << (low- v.begin()) << '
';
  std::cout << "upper_bound at position " << (up - v.begin()) << '
';

  return 0;
}

lower bound c++

The lower_bound() method in C++ is used to return an iterator pointing to the first element in the range [first, last) which has a value not less than val.