title: Divide and conquer strategy python
body: <p>I am trying to write a code which to compare each element of a list and give the index of the closet larger number in two direction: left or right. Using the divide and conquer method</p>
  
  <pre><code>For example:
  
  Input: arr=[5,2,6,8,1,4,3,9]
  Output:
  Left=[None, 0, None, None, 3, 3, 5, None]
  Right=[2, 2, 3, 7, 5, 7, 7, None]
  
  Input: arr=[4,2,3,1,8,5,6,9]
  Output:
  L=[None, 0, 0, 2, None, 4, 4, None]
  R=[4, 2, 4, 4, 7, 6, 7, None]
  </code></pre>
  
  <p>This is what I have now:</p>
  
  <pre><code>arr = [5,2,6,8,1,4,3,9]
  def Left(arr):
      L = []
      for i in range(len(arr)):
          flag = True
          for j in range(i,-1,-1):
              if (arr[i] &lt; arr[j]):
                  L.append(j)
                  flag = False
                  break
          if flag:
              L.append(None)
      return L
  
  def Right(arr):
      R = []
      for i in range(len(arr)):
          flag = True
          for j in range(i, len(arr), 1):
              if (arr[i] &lt; arr[j]):
                  R.append(j)
                  flag = False
                  break
          if flag:
                  R.append(None)
      return R
  
  print(*Left(arr), sep = ",")
  print(*Right(arr), sep =",")
  </code></pre>
  
  <p>Am I doing it in a right way? Thank you.</p>