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POHow to replace <key, value> in a std multimap
 

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  1. POHow to replace <key, value> in a std multimap
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    <p>Rehrasing the question - Question rephrased - I have a requirement where I need to replace a pair with a new key and value. Consider this - </p> <pre><code>#include &lt;map&gt; #include &lt;string&gt; #include &lt;iostream&gt; using namespace std; int main() { std::multimap&lt;unsigned int, std::string&gt; mymap; mymap.insert(std::multimap&lt;unsigned int, std::string&gt;::value_type(0, "A1")); mymap.insert(std::multimap&lt;unsigned int, std::string&gt;::value_type(0, "A2")); mymap.insert(std::multimap&lt;unsigned int, std::string&gt;::value_type(2, "C1")); mymap.insert(std::multimap&lt;unsigned int, std::string&gt;::value_type(2, "C2")); mymap.insert(std::multimap&lt;unsigned int, std::string&gt;::value_type(1, "B1")); mymap.insert(std::multimap&lt;unsigned int, std::string&gt;::value_type(1, "B2")); mymap.insert(std::multimap&lt;unsigned int, std::string&gt;::value_type(1, "B3")); std::pair&lt;std::multimap&lt;unsigned int, std::string&gt;::iterator, std::multimap&lt;unsigned int, std::string&gt;::iterator&gt; pr = mymap.equal_range(1); std::multimap&lt;unsigned int, std::string&gt;::iterator it; for (it=pr.first; it!=pr.second; ++it) { unsigned int key = it-&gt;first; key = key+10; std::string val = it-&gt;second; val = "X" + val; mymap.erase(it); mymap.insert(std::multimap&lt;unsigned int, std::string&gt;::value_type(key, val)); } for ( it=mymap.begin() ; it != mymap.end(); it++ ) { cout &lt;&lt; (*it).first &lt;&lt; " =&gt; " &lt;&lt; (*it).second &lt;&lt; endl; } return 0; } </code></pre> <p>The program crashes on visual studio 2008 since the iterator is invalidated.</p> <p>I expect it to be:</p> <pre><code>0 =&gt; A1 0 =&gt; A2 2 =&gt; C1 2 =&gt; C2 11 =&gt; XB1 11 =&gt; XB2 11 =&gt; XB3 </code></pre> <p>The idea is I want to replace an existing entry in the map with a new entry.</p> <p>What am I doing wrong? Any help very much appreciated.</p>
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