Implementation of lower_bound() and upper_bound() in Vector of Pairs in C++
Here we will discuss the implementation of the lower_bound() and upper_bound() in vector of pairs.
lower_bound():
It returns an iterator pointing to the first element in the range [first, last) which has a value greater than or equal to the given value “val”. But in Vector of Pairs lower_bound() for pair(x, y) will return an iterator pointing to the position of pair whose
- first value is greater than x
- first value is equal to x and second value is greater than equals to y.
If the above-mentioned criteria are not met, then it returns an iterator to the index which is out of the vectors of pairs.
upper_bound():
It returns an iterator pointing to the first element in the range [first, last) which has a value greater than the given value “val”. But in Vector of Pairs upper_bound() for pair(x, y) will return an iterator pointing to the position of the pair whose
- First value is equal to x and the second value is greater than y, or
- Whose first value is greater than x.
Below is the program to demonstrate lower_bound() and upper_bound() in vector of pairs:
Program 1:
CPP
// C++ program to demonstrate lower_bound() // and upper_bound() in Vectors of Pairs #include <bits/stdc++.h> using namespace std; // Function to implement lower_bound() void findLowerBound(vector<pair< int , int > >& arr, pair< int , int >& p) { // Given iterator points to the // lower_bound() of given pair auto low = lower_bound(arr.begin(), arr.end(), p); cout << "lower_bound() for {2, 5}" << " is at index: " << low - arr.begin() << endl; } // Function to implement upper_bound() void findUpperBound(vector<pair< int , int > >& arr, pair< int , int >& p) { // Given iterator points to the // upper_bound() of given pair auto up = upper_bound(arr.begin(), arr.end(), p); cout << "upper_bound() for {2, 5}" << " is at index: " << up - arr.begin() << endl; } // Driver Code int main() { // Given sorted vector of Pairs vector<pair< int , int > > arr; arr = { { 1, 3 }, { 1, 7 }, { 2, 4 }, { 2, 5 }, { 3, 8 }, { 8, 6 } }; // Given pair {2, 5} pair< int , int > p = { 2, 5 }; // Function Call to find lower_bound // of pair p in arr findLowerBound(arr, p); // Function Call to find upper_bound // of pair p in arr findUpperBound(arr, p); return 0; } |
lower_bound() for {2, 5} is at index: 3 upper_bound() for {2, 5} is at index: 4