title: how to get indexes of an array element starting with a letter in ios?
body: <p>I want to get indexes of an array starting with particular letter,
  Example: i have an array </p>
  
  <p><code>NSArray *arr = @[@"apple", @"aghf", @"chg", @"dee", @"ijh", @"inbv", @"khh"];</code></p>
  
  <p>how to get the indexes of array elements starting with "a"? </p>
  
  <p>In the case if it is 0 and 1, how to get both the values? please help</p>