set::find

2015-07-29

Returns an iterator that refers to the ___location of an element in a set that has a key equivalent to a specified key.

iterator find(const Key& key);

const_iterator find(const Key& key) const;

Parameters

key
The key value to be matched by the sort key of an element from the set being searched.

Return Value

An iterator that refers to the ___location of an element with a specified key, or the ___location succeeding the last element in the set (set::end()) if no match is found for the key.

Remarks

The member function returns an iterator that refers to an element in the set whose key is equivalent to the argument key under a binary predicate that induces an ordering based on a less than comparability relation.

If the return value of find is assigned to a const_iterator, the set object cannot be modified. If the return value of find is assigned to an iterator, the set object can be modified

Example

// compile with: /EHsc /W4 /MTd
#include <set>
#include <iostream>
#include <vector>
#include <string>

using namespace std;

template <typename T> void print_elem(const T& t) {
    cout << "(" << t << ") ";
}

template <typename T> void print_collection(const T& t) {
    cout << t.size() << " elements: ";

    for (const auto& p : t) {
        print_elem(p);
    }
    cout << endl;
}

template <typename C, class T> void findit(const C& c, T val) {
    cout << "Trying find() on value " << val << endl;
    auto result = c.find(val);
    if (result != c.end()) {
        cout << "Element found: "; print_elem(*result); cout << endl;
    } else {
        cout << "Element not found." << endl;
    }
}

int main()
{
    set<int> s1({ 40, 45 });
    cout << "The starting set s1 is: " << endl;
    print_collection(s1);

    vector<int> v;
    v.push_back(43);
    v.push_back(41);
    v.push_back(46);
    v.push_back(42);
    v.push_back(44);
    v.push_back(44); // attempt a duplicate

    cout << "Inserting the following vector data into s1: " << endl;
    print_collection(v);

    s1.insert(v.begin(), v.end());

    cout << "The modified set s1 is: " << endl;
    print_collection(s1);
    cout << endl;
    findit(s1, 45);
    findit(s1, 6);
}

Output

The starting set s1 is:
2 elements: (40) (45)
Inserting the following vector data into s1:
6 elements: (43) (41) (46) (42) (44) (44)
The modified set s1 is:
7 elements: (40) (41) (42) (43) (44) (45) (46)

Trying find() on value 45
Element found: (45)
Trying find() on value 6
Element not found.

Requirements

Header: <set>

Namespace: std

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