How to use the search() function in C++
The search() function in C++ helps search for a sequence of elements inside an array/vector. This function is available in the <algorithm.h> header file.
Parameters
The search() function accepts the following parameters:
-
first1, last1: These are the iterators pointing to the initial and final positions of the array/vector where the search operation needs to be performed. -
first2, last2: These are the iterators pointing to the initial and final positions of the array/vector that needs to be searched. -
pred: This is an optional parameter that specifies a binary function that returns a boolean value, which indicates how to perform the search.
Return value
The search() function returns an iterator that points to the first occurrence of the sequence in the range [first2, last2) in the sequence [first1, last1). If the value is not found, then it returns an iterator to last1 of the array or vector.
Code
Let’s take a look at the code.
#include <iostream>#include <algorithm>#include <vector>using namespace std;int main () {vector<int> vec;for (int i = 1; i <= 10; i++)vec.push_back(i*10);int seq[] = {40,50,60,70};auto it = search(vec.begin(), vec.end(), seq, seq + 4);if (it!=vec.end())cout << "Sequence found at position " << (it-vec.begin());elsecout << "Sequence not found";return 0;}
Explanation
- In lines 1 to 3, we import the required libraries.
- In lines 7 to 9, we create a vector with some integer values.
- In line 11, we define the sequence that we want to search in the vector.
- In line 12, we call the
search()function and pass all the required parameters. - In line 14, we check whether the sequence is found or not. If the sequence is not found, then the value of
itpoints to the end of the vector. - In line 15, we print the index from where the sequence starts.
- In line 17, we print if the sequence is not found.
Now, let us look at code where we use a binary predicate to perform the search.
#include <iostream>#include <vector>#include <algorithm>using namespace std;bool pred (int i, int j) {return (i==j);}int main() {vector<int> vec;for (int i = 1; i <= 10; i++)vec.push_back(i*10);int seq[] = {20,30,50};auto it = search (vec.begin(), vec.end(), seq, seq + 3, pred);if (it!=vec.end())cout << "Sequence found at position " << (it-vec.begin());elsecout << "Sequence not found";return 0;}
Explanation
- In lines 1 to 3, we import the required libraries.
- In lines 6 to 8, we create a binary function that accepts two integers and returns a boolean value.
- In lines 12 to 14, we create a vector with some integer values.
- In line 16, we define the sequence that we want to search in the vector.
- In line 15, we call the
search()function and pass all the required parameters. - In line 19, we check whether the sequence is found or not. If the sequence is not found, then the value of
itpoints to the end of the vector. - In line 20, we print the index from where the sequence starts.
- In line 22, we print if the sequence is not found.
