The search function in C++ Algorithm scans the specified range [first1, last1) to find a subsequence defined by the range [first2, last2), and it returns an iterator pointing to the initial element of the subsequence. If the subsequence is not found, it returns an iterator pointing to the last element of the range [first1, last1).
Syntax
template<class ForwardIterator1, class ForwardIterator2> ForwardIterator1 search (ForwardIterator1 first1, ForwardIterator last1, ForwardIterator2 first2, ForwardIterator2 last2);
template<class ForwardIterator1, class ForwardIterator2, class BinaryPredicate> ForwardIterator1 search(ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2, BinaryPredicate pred);
Parameter
It serves as a forward iterator pointing to the initial element within the [first1, last1) range.
It serves as a forward iterator pointing to the final element within the range specified by [first1, last1).
It represents a forward iterator pointing to the initial element within the range defined by [first2, last2).
pred : It is a binary function that takes in two elements as parameters and executes the specified task within the function.
Return value
The function will provide an iterator pointing to the initial element of the first instance of the subsequence. If the subsequence is not found, it will return an iterator pointing to the last element in the sequence.
Example 1
#include <iostream>
#include <algorithm>
#include <vector>
bool newpredicate (int m, int n)
{
return (m==n);
}
int main ()
{
std::vector<int> haystack;
for (int a=1; a<10; a++) haystack.push_back(a*10);
int patt1[] = {20,30,40,50};
std::vector<int>::iterator ti;
ti = std::search (haystack.begin(), haystack.end(), patt1, patt1+4);
if (ti!=haystack.end())
std::cout << "patt1 found at position " << (ti-haystack.begin()) << '\n';
else
std::cout << "patt1 not found\n";
int patt2[] = {40,35,50};
ti = std::search (haystack.begin(), haystack.end(), patt2, patt2+3, newpredicate);
if (ti!=haystack.end())
std::cout << "patt2 found at position " << (ti-haystack.begin()) << '\n';
else
std::cout << "patt2 not found\n";
return 0;
}
Output:
patt1 found at position 1
patt2 not found
Example 2
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
int main()
{
int m, n;
vector <int> u1={1,2,3,4,5,6,7};
vector <int> u2={3,4,5};
vector<int>::iterator ti;
ti = std::search(u1.begin(), u1.end(), u2.begin(),u2.end());
if(ti!=u1.end())
{
cout<<"Vector2 is present at index:"<<(ti-u1.begin());
}
else
{
cout<<"In vector1, vector2 is not present";
}
return 0;
}
Output:
Vector2 is present at index:2
Complexity
The function exhibits a linear time complexity from the initial element to the final element.
Data races
Objects in both ranges are accessed.
Exceptions
The function will raise an exception if any of its arguments also raises an exception.
