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POHow to contain my class with std::set
 

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  1. POHow to contain my class with std::set
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    <p>I'm trying to write a program in C++ language.</p> <p>Class Edge indicates the connection between u and v.</p> <p>Edge a which indicates the connection between u and v. Edge a' which indicates the connection between v and u. Edge a and a' indicate same connection. So, I want to contain either a or a'.</p> <p>I know "set" stores unique elements. So I want to use this. I define operator&lt; below.</p> <p>When I search bugs, I found some trubles. I store (1,2) -> (1,2) -> (2,1) -> (3,2) -> (2,3) -> (5,2). </p> <p>But set stores</p> <pre><code>1 2 5 2 3 2 1 2 &lt;-- Why ???? </code></pre> <p>Could you help me??</p> <pre><code>#include&lt;iostream&gt; #include&lt;set&gt; class Edge { private: int u, v; public: bool operator&lt; (const Edge&amp; e) const { bool result = true; if( (u == e.u &amp;&amp; v == e.v) || (v == e.u &amp;&amp; u == e.v) ) { result = false; } return result; } std::pair&lt;int, int&gt; pair() const { return std::pair&lt;int, int&gt;(u, v); } Edge(int u_, int v_) : u(u_), v(v_) {} }; int main(void) { std::set&lt;Edge&gt; edge; std::set&lt;Edge&gt;::iterator eit; edge.insert(Edge(1,2)); // &lt;-- (1,2) can be contained. edge.insert(Edge(1,2)); // &lt;-- (1,2) doesn't have to be contained. edge.insert(Edge(2,1)); // &lt;-- (2,2) doesn't have to be contained. edge.insert(Edge(3,2)); // &lt;-- (3,2) can be contained. edge.insert(Edge(2,3)); // &lt;-- (2,3) doesn't have to be contained. edge.insert(Edge(5,2)); // &lt;-- (5,2) doesn't have to be contained. edge.insert(Edge(1,2)); // &lt;-- (1,2) doesn't have to be contained. But edge contains this. Why? for(eit = edge.begin(); eit != edge.end(); eit++) { std::cout &lt;&lt; (*eit).pair().first &lt;&lt; " " &lt;&lt; (*eit).pair().second &lt;&lt; std::endl; } return 0; } </code></pre>
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