title: error: no viable conversion from char to string
body: <pre class="lang-cpp prettyprint-override"><code>int num = digits[i]-'0';
  string value = map[num];
  
  for(int j=0;j&lt;value.length();j++)
  {
      output.push_back(value[i]);
      solve(digits,ans,output,map,i+1);
      output.pop_back();
  }
  </code></pre>
  <p>For the above code, I got this error:</p>
  <pre class="lang-none prettyprint-override"><code>Line 12: Char 16: error: no viable conversion from '__gnu_cxx::__alloc_traits&lt;std::allocator&lt;char&gt;, char&gt;::value_type' (aka 'char') to 'std::string' (aka 'basic_string&lt;char&gt;')
          string value = map[num];
                 ^       ~~~~~~~~
  </code></pre>