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C++ map rend() Funkcija

C++ karte renderēt () funkcija tiek izmantota, lai atgrieztu iteratoru kartes beigās (nevis pēdējais elements, bet gan pagātnes pēdējais elements). apgrieztā secībā . Tas ir līdzīgs elementam, kas atrodas pirms pirmā neapgrieztā konteinera elementa.

Piezīme:- Šis ir vietturis. Šajā vietā nav neviena elementa, un mēģinājums piekļūt ir nenoteikta darbība.

Sintakse

 reverse_iterator rend(); //until C++ 11 const_reverse_iterator rend() const; //until C++ 11 reverse_iterator rend() noexcept; //since C++ 11 const_reverse_iterator rend() const noexcept; //since C++ 11

Parametrs

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Atdeves vērtība

Tas atgriež reverso iteratoru elementam, kas seko apgrieztā konteinera pēdējam elementam.

1. piemērs

Apskatīsim vienkāršu funkcijas rend() piemēru:

 #include #include using namespace std; int main () { map mymap; mymap[&apos;x&apos;] = 100; mymap[&apos;y&apos;] = 200; mymap[&apos;z&apos;] = 300; // show content: map::reverse_iterator rit; for (rit=mymap.rbegin(); rit!=mymap.rend(); ++rit) cout <first << '=" &lt;second &lt;&lt; " 
'; return 0; } < pre> <p> <strong>Output:</strong> </p> <pre> z = 300 y = 200 x = 100 </pre> <p>In the above example, rend() function is used to return a reverse iterator to the element following the last element of the reversed container.</p> <p>Because map store the elements in sorted order of keys therefore, iterating over a map will result in above order i.e. sorted order of keys.</p> <h2>Example 2</h2> <p>Let&apos;s see a simple example to iterate over the map in reverse order using while loop:</p> <pre> #include #include #include #include using namespace std; int main() { // Creating &amp; Initializing a map of String &amp; Ints map mapEx = { { &apos;aaa&apos;, 10 }, { &apos;ddd&apos;, 11 }, { &apos;bbb&apos;, 12 }, { &apos;ccc&apos;, 13 } }; // Create a map iterator and point to the end of map map::reverse_iterator it = mapEx.rbegin(); // Iterate over the map using Iterator till beginning. while (it != mapEx.rend()) { // Accessing KEY from element pointed by it. string word = it-&gt;first; // Accessing VALUE from element pointed by it. int count = it-&gt;second; cout &lt;&lt; word &lt;&lt; &apos; :: &apos; &lt;&lt; count &lt;&lt; endl; // Increment the Iterator to point to next entry it++; } return 0; } </pre> <p> <strong>Output:</strong> </p> <pre> ddd :: 11 ccc :: 13 bbb :: 12 aaa :: 10 </pre> <p>In the above example, we are using while loop to iterate over the map in reverse order.</p> <p>Because map store the elements in sorted order of keys therefore, iterating over a map will result in above order i.e. sorted order of keys.</p> <h2>Example 3</h2> <p>Let&apos;s see a simple example.</p> <pre> #include #include using namespace std; int main(void) { /* Initializer_list constructor */ map m = { {&apos;a&apos;, 1}, {&apos;b&apos;, 2}, {&apos;c&apos;, 3}, {&apos;d&apos;, 4}, {&apos;e&apos;, 5}, }; cout &lt;&lt; &apos;Map contains following elements in reverse order:&apos; &lt;&lt; endl; for (auto it = m.rbegin(); it != m.rend(); ++it) cout <first << '=" &lt;second &lt;&lt; endl; return 0; } &lt;/pre&gt; &lt;p&gt; &lt;strong&gt;Output:&lt;/strong&gt; &lt;/p&gt; &lt;pre&gt; Map contains following elements in reverse order: e = 5 d = 4 c = 3 b = 2 a = 1 &lt;/pre&gt; &lt;p&gt;In the above example, elements of map returned in a reverse order.&lt;/p&gt; &lt;h2 &gt;Example 4&lt;/h2&gt; &lt;p&gt;Let" s see a simple example to sort and calculate the highest marks.< p> <pre> #include #include #include using namespace std; int main () { map emp = { { 1000, 10}, { 2500, 20 }, { 4500, 30 }, { 3000, 40 }, { 5500, 50 }}; cout &lt;&lt; &apos;Salary&apos; &lt;&lt; &apos; | &apos; &lt;&lt; &apos;ID&apos; &lt;&lt; &apos;
&apos;; cout&lt;<'______________________
'; map::reverse_iterator rit; for (rit="emp.rbegin();" rit!="emp.rend();" ++rit) cout <first << ' | <second '
'; auto ite="emp.rbegin();" '
highest salary: '<first <<' 
'; 'id is: '<second return 0; } < pre> <p> <strong>Output:</strong> </p> <pre> Salary | ID ______________________ 5500 | 50 4500 | 30 3000 | 40 2500 | 20 1000 | 10 Highest salary: 5500 ID is: 50 </pre> <p>In the above example, a map emp is implemented where the ID is being stored as value and salary as key. This enables us to take advantage of the auto sorting in maps and lets us to identify the ID of the element with the highest salary.</p></'______________________
';></pre></first></pre></first>

Iepriekš minētajā piemērā funkcija rend() tiek izmantota, lai atgrieztu reverso iteratoru elementam, kas seko apgrieztā konteinera pēdējam elementam.

javascript datums

Tā kā kartē elementi tiek glabāti sakārtotā atslēgu secībā, atkārtojot karti, tiks parādīta augstāka secība, t.i., sakārtota atslēgu secība.

2. piemērs

Apskatīsim vienkāršu piemēru, kā atkārtot karti apgrieztā secībā, izmantojot cilpu while:

 #include #include #include #include using namespace std; int main() { // Creating &amp; Initializing a map of String &amp; Ints map mapEx = { { &apos;aaa&apos;, 10 }, { &apos;ddd&apos;, 11 }, { &apos;bbb&apos;, 12 }, { &apos;ccc&apos;, 13 } }; // Create a map iterator and point to the end of map map::reverse_iterator it = mapEx.rbegin(); // Iterate over the map using Iterator till beginning. while (it != mapEx.rend()) { // Accessing KEY from element pointed by it. string word = it-&gt;first; // Accessing VALUE from element pointed by it. int count = it-&gt;second; cout &lt;&lt; word &lt;&lt; &apos; :: &apos; &lt;&lt; count &lt;&lt; endl; // Increment the Iterator to point to next entry it++; } return 0; }

Izvade: 

 ddd :: 11 ccc :: 13 bbb :: 12 aaa :: 10

Iepriekš minētajā piemērā mēs izmantojam cilpu while, lai iterētu karti apgrieztā secībā.

Tā kā kartē elementi tiek glabāti sakārtotā atslēgu secībā, atkārtojot karti, tiks parādīta augstāka secība, t.i., sakārtota atslēgu secība.

3. piemērs

Apskatīsim vienkāršu piemēru.

vba 
 #include #include using namespace std; int main(void) { /* Initializer_list constructor */ map m = { {&apos;a&apos;, 1}, {&apos;b&apos;, 2}, {&apos;c&apos;, 3}, {&apos;d&apos;, 4}, {&apos;e&apos;, 5}, }; cout &lt;&lt; &apos;Map contains following elements in reverse order:&apos; &lt;&lt; endl; for (auto it = m.rbegin(); it != m.rend(); ++it) cout <first << \'=" &lt;second &lt;&lt; endl; return 0; } &lt;/pre&gt; &lt;p&gt; &lt;strong&gt;Output:&lt;/strong&gt; &lt;/p&gt; &lt;pre&gt; Map contains following elements in reverse order: e = 5 d = 4 c = 3 b = 2 a = 1 &lt;/pre&gt; &lt;p&gt;In the above example, elements of map returned in a reverse order.&lt;/p&gt; &lt;h2 &gt;Example 4&lt;/h2&gt; &lt;p&gt;Let" s see a simple example to sort and calculate the highest marks.< p> <pre> #include #include #include using namespace std; int main () { map emp = { { 1000, 10}, { 2500, 20 }, { 4500, 30 }, { 3000, 40 }, { 5500, 50 }}; cout &lt;&lt; &apos;Salary&apos; &lt;&lt; &apos; | &apos; &lt;&lt; &apos;ID&apos; &lt;&lt; &apos;
&apos;; cout&lt;<\'______________________
\'; map::reverse_iterator rit; for (rit="emp.rbegin();" rit!="emp.rend();" ++rit) cout <first << \' | <second \'
\'; auto ite="emp.rbegin();" \'
highest salary: \'<first <<\' 
\'; \'id is: \'<second return 0; } < pre> <p> <strong>Output:</strong> </p> <pre> Salary | ID ______________________ 5500 | 50 4500 | 30 3000 | 40 2500 | 20 1000 | 10 Highest salary: 5500 ID is: 50 </pre> <p>In the above example, a map emp is implemented where the ID is being stored as value and salary as key. This enables us to take advantage of the auto sorting in maps and lets us to identify the ID of the element with the highest salary.</p></\'______________________
\';></pre></first>

Iepriekš minētajā piemērā ir ieviests kartes emp, kur ID tiek saglabāts kā vērtība un alga kā atslēga. Tas ļauj mums izmantot automātiskās šķirošanas priekšrocības kartēs un ļauj mums identificēt elementa ID ar lielāko algu.