C++ algorithm search() function

by Online Tutorials Library July 22, 2022

C++ Algorithm Function search()

C++ Algorithm search() function searches the range [first1, last1) for the occurrence of a subsequence defined by the range [first2, last2), and an iterator to the first element is returned. If the subsequence does not exist then an iterator to the last1 is returned.

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

first1: It is a forward iterator to the first element of the [first1, last1).

last1: It is a forward iterator to the last element of the [first1, last1).

first2: It is a forward iterator to the first element of the [first2, last2).

pred: It is a binary function that accepts two elements as arguments and performs the task designed by the function.

Return value

The function returns an iterator to the first element of the first occurrence of the subsequence, else returns the last1 element.

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 foundn”;    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 foundn”;    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 has linear complexity from the first1 element to the last1 element.

Data races

Objects in both ranges are accessed.

Exceptions

The function throws an exception if any of the argument throws one.

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