2.10 Implementing String Algorithms

1. Exam Points

• Algorithms to manipulate strings
  • find if one or more substrings have a particular property
  • determine the number of substrings that meet specific criteria
  • create a new string with the characters reversed
• Note:
  • Use specific example values when necessary.
  • Index of a string starts with 0 and ends with length-1
  • Valid index: 0 to length
  • An index of -1 or > length will cause errors (IndexOutOfBoundsException)
  • Get 1 characters: substring(index, index + 1)
  • Get n characters: substring(index, index + n)

2. Knowledge Points

(1) Implementing String Algorithms

• Pay attention when manipulating strings:
  • get EF from string ABEF
    • str.substring(2,4)
  • valid index in string ABEF
    • 0 to 4 (0 to length)
  • invalid index: index<0 or index>length
  • get one character
    • str.substring(i, i+1)
  • get n characters
    • str.substring(i, i+n)
• There are standard string algorithms to:
  • 1. find if one or more substrings have a particular property
    • Ex. count consecutive pairs in a string : abbcdddeff
  • 2. determine the number of substrings that meet specific criteria
    • Ex. determine the number of ABCs in string ABCdeABCffABC
  • 3. create a new string with the characters reversed
    • Ex. print the reversed string of ABCD, that is DCBA

3. Exercises

• Practice
• Solution