text: # https://www.lintcode.com/problem/implement-strstr/description?_from=ladder&&fromId=1
  # Time Complexity O(mn)
  # Space Complexity O(1)
  class Solution:
      """
      @param source: 
      @param target: 
      @return: return the index
      """
  
      def strStr(self, source, target):
          l1 = len(source)
          l2 = len(target)
  
          for i in range(l1 - l2 + 1):
              if source[i:i+l2] == target:
                  return i
          return -1
  