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add c++ language notes
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‎Makefile‎

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DIRS_UNSORTED= rpi \
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linux \
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brave_browser \
4-
c
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c \
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cpp
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DIRS=$(sort $(DIRS_UNSORTED))
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‎README.md‎

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- [brave_browser](brave_browser/brave_browser_notes.md)
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- [c](c/c_notes.md)
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- [cpp](cpp/cpp_notes.md)
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- [linux](linux/linux_notes.md)
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- [rpi](rpi/rpi_notes.md)
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‎build.sh‎

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# AUTOGENERATED!! DO NOT EDIT
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make NOTE_NAME=brave_browser_notes -C brave_browser -f brave_browser.mk --no-print-directory
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make NOTE_NAME=c_notes -C c -f c.mk --no-print-directory
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make NOTE_NAME=cpp_notes -C cpp -f cpp.mk --no-print-directory
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make NOTE_NAME=linux_notes -C linux -f linux.mk --no-print-directory
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make NOTE_NAME=rpi_notes -C rpi -f rpi.mk --no-print-directory

‎cpp/cpp.mk‎

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# AUTOGENERATED!! DO NOT EDIT
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include ../constants.mk
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include ../common.mk

‎cpp/cpp_notes.html‎

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<!DOCTYPE html>
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<html>
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<head>
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<meta charset="utf-8" />
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<meta name="viewport" content="width=device-width,initial-scale=1" />
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<meta name="author" content="devpogi" />
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<link rel="stylesheet" href="../style.css" />
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<title>devpogi notes</title>
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</head>
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<body>
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<header>
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<a href="../index.html">Home</a>
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</header>
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<h1 id="c-notes">C++ notes</h1>
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<h2 id="custom-compare-function-for-custom-objects">Custom compare function for custom objects</h2>
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<pre><code class="language-cpp">&#47;&#47; using custom compare function for custom objects in priority_queue
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#include &#60;iostream&#62;
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#include &#60;queue&#62;
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using namespace std;
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struct Node
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{
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int a;
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int b;
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};
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bool compare(const Node &#38;n, const Node &#38;m)
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{
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if (n.a &#60; m.a)
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return true;
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else if (n.a == m.a)
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{
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if (n.b &#60; m.b)
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return true;
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}
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return false;
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}
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priority_queue&#60;Node, vector&#60;Node&#62;, decltype(&#38;compare)&#62; buff(compare);
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int main()
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{
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Node arr[] = {{2, 3}, {2, 4}, {2, 1}, {3, 1}, {3, 5}, {1, 3}, {1, 4}, {1, 0}};
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for (int i = 0; i &#60; sizeof(arr) &#47; sizeof(arr[0]); i++)
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{
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buff.push(arr[i]);
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}
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while (!buff.empty())
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{
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cout &#60;&#60; "{" &#60;&#60; buff.top().a &#60;&#60; "," &#60;&#60; buff.top().b &#60;&#60; "}\n";
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buff.pop();
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}
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return 0;
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}
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&#47;*
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OUTPUT -
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{3,5}
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{3,1}
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{2,4}
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{2,3}
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{2,1}
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{1,4}
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{1,3}
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{1,0}
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*&#47;
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</code></pre>
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<h2 id="optimization-reserve-the-size-of-hash-table">Optimization: reserve the size of hash table</h2>
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<pre><code class="language-cpp">#define SIZE_OF_HASH_TABLE 20000
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unordered_map&#60;string, int&#62; mymap;
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mymap.reserve(SIZE_OF_HASH_TABLE);
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</code></pre>
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<p>This reserves the size of the hash table so that re-hashing doesn&#8217;t occur for at least till <code>SIZE_OF_HASH_TABLE</code> number of elememts. </p>
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</body>
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</html>

‎cpp/cpp_notes.md‎

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# C++ notes
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## Custom compare function for custom objects
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```cpp
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// using custom compare function for custom objects in priority_queue
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#include <iostream>
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#include <queue>
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using namespace std;
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struct Node
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{
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int a;
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int b;
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};
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bool compare(const Node &n, const Node &m)
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{
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if (n.a < m.a)
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return true;
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else if (n.a == m.a)
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{
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if (n.b < m.b)
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return true;
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}
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return false;
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}
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priority_queue<Node, vector<Node>, decltype(&compare)> buff(compare);
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int main()
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{
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Node arr[] = {{2, 3}, {2, 4}, {2, 1}, {3, 1}, {3, 5}, {1, 3}, {1, 4}, {1, 0}};
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for (int i = 0; i < sizeof(arr) / sizeof(arr[0]); i++)
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{
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buff.push(arr[i]);
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}
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while (!buff.empty())
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{
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cout << "{" << buff.top().a << "," << buff.top().b << "}\n";
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buff.pop();
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}
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return 0;
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}
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/*
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OUTPUT -
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{3,5}
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{3,1}
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{2,4}
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{2,3}
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{2,1}
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{1,4}
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{1,3}
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{1,0}
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*/
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```
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## Optimization: reserve the size of hash table
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```cpp
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#define SIZE_OF_HASH_TABLE 20000
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unordered_map<string, int> mymap;
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mymap.reserve(SIZE_OF_HASH_TABLE);
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```
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This reserves the size of the hash table so that re-hashing doesn't occur for at least till `SIZE_OF_HASH_TABLE` number of elememts.
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‎index.html‎

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<ul>
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<li><a href="brave_browser/brave_browser_notes.html">brave_browser</a></li>
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<li><a href="c/c_notes.html">c</a></li>
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<li><a href="cpp/cpp_notes.html">cpp</a></li>
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<li><a href="linux/linux_notes.html">linux</a></li>
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<li><a href="rpi/rpi_notes.html">rpi</a></li>
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</ul>

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