title: how to explain this? A "new"-ed array is not initialized...?
body: <p>I met something strange : an array "new"-ed in heap with random values...</p>
  
  <p>I did a test with codes below:</p>
  
  <pre><code>class Solution_046 {
  public:
      vector&lt;vector&lt;int&gt;&gt; permute(vector&lt;int&gt;&amp; nums) {
          vector&lt;vector&lt;int&gt;&gt; rst;
          int sz = nums.size();
          if(sz)
          {
              vector&lt;int&gt; group;
              int* inuse = new int[sz];
              cout&lt;&lt;"--------- inuse ------------"&lt;&lt;endl;
              for(int ii=0; ii&lt;sz; ++ii)
                  //inuse[ii]=0, cout&lt;&lt;inuse[ii]&lt;&lt;", ";
                  cout&lt;&lt;inuse[ii]&lt;&lt;",, ";
              cout&lt;&lt;endl;
  
              //......
          }
          return rst;
      }
  };
  
  
  int main()
  {
      Solution_046 s046;
      vector&lt;int&gt; vv;
      vv.push_back(1);
      vv.push_back(2);
      vv.push_back(3);
      vv.push_back(4);
      vv.push_back(5);
      vv.push_back(6);
      vv.push_back(7);
      vector&lt; vector&lt;int&gt; &gt; rst = s046.permute(vv);
      return 0;
  }
  </code></pre>
  
  <p>If I disable one or two lines of those "vv.push_back(...)", then the result printed will include some random value instead of all zeros:</p>
  
  <pre><code>$ ./nc (with all 7 lines)
  --------- inuse ------------
  0,, 0,, 0,, 0,, 0,, 0,, 0,, 
  
  $ ./nc (disalbed one line)
  --------- inuse ------------
  29339680,, 0,, 4,, 5,, 0,, 0,, 
  
  $ ./nc (disabled two lines)
  --------- inuse ------------
  26095648,, 0,, 5,, 6,, 0,, 
  
  $ ./nc (disabled three lines)
  --------- inuse ------------
  0,, 0,, 0,, 0,, 
  
  $ ./nc (disabled four lines)
  --------- inuse ------------
  0,, 0,, 0,, 0,, 
  
  $ ./nc (disabled five lines)
  --------- inuse ------------
  0,, 0,,
  
  $ ./nc (disabled six lines)
  --------- inuse ------------
  0,,
  </code></pre>
  
  <p>What happened while disabling one or two lines, why there are non-zero values in the "new"-ed array? </p>