C++ STL中的unordered_multimap find()函数

unordered_multimap :: find()是C++ STL中的内置函数，该函数返回一个迭代器，该迭代器指向具有键k的元素之一。如果容器不包含键为k的任何元素，则它将返回一个迭代器，该迭代器指向该容器中最后一个元素之后的位置。

句法：

unordered_multimap_name.find(k)

参数：该函数接受一个必填参数k ，该参数指定了密钥。

返回值：它返回一个迭代器，该迭代器指向具有键k的元素所在的位置。

下面的程序说明了上述函数：

程序1：

// C++ program to illustrate the
// unordered_multimap::find() function
#include 
#include 
using namespace std;
  
int main()
{
  
    // declaration
    unordered_multimap sample;
  
    // inserts key and element
    sample.insert({ 1, 2 });
    sample.insert({ 1, 2 });
    sample.insert({ 2, 3 });
    sample.insert({ 3, 4 });
    sample.insert({ 2, 6 });
  
    // find the element with key 1 and print
    auto it = sample.find(1);
    if (it != sample.end())
        cout << 1 << ":" << it->second << endl;
    else
        cout << "element with key 1 not found\n";
  
    // find the element with
    // key 2 and print
    it = sample.find(2);
    if (it != sample.end())
        cout << 2 << ":" << it->second << endl;
    else
        cout << "element with key 2 not found\n";
  
    // find the element with
    // key 100 and print
    it = sample.find(100);
    if (it != sample.end())
        cout << 100 << ":" << it->second << endl;
    else
        cout << "element with key 100 not found\n";
    return 0;
}

输出：

1:2
2:6
element with key 100 not found

程式2：

// C++ program to illustrate the
// unordered_multimap::find()
#include 
#include 
using namespace std;
  
int main()
{
  
    // declaration
    unordered_multimap sample;
  
    // inserts element
    sample.insert({ 'a', 'b' });
    sample.insert({ 'a', 'b' });
    sample.insert({ 'a', 'd' });
    sample.insert({ 'b', 'e' });
    sample.insert({ 'b', 'd' });
  
    // find the element with
    // key r and print
    auto it = sample.find('r');
    if (it != sample.end())
        cout << "r"
             << ":" << it->second << endl;
    else
        cout << "element with key r not found\n";
  
    // find the element with
    // key a and print
    it = sample.find('a');
    if (it != sample.end())
        cout << 'a' << ":" << it->second << endl;
    else
        cout << "element with key a not found\n";
  
    // find the element with
    // key 'b' and print
    it = sample.find('b');
    if (it != sample.end())
        cout << "b"
             << ":" << it->second << endl;
    else
        cout << "element with key b not found\n";
  
    return 0;
}

输出：

element with key r not found
a:d
b:d

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