palindrome: Use string slice instead of concatenating, this makes the code WAY faster

Dependencies

• [2] VUXCDW3L palindrome: move to palindrome package
• [3] O64GEJAP palindrome: do not report one char long palindromes
• [4] ZQFONDI4 Add simple version
• [*] MCHVA5DY Palindrome initial import

Change contents

• replacement in snippets/palindrome/palindrome.go at line 9
  [2.173]→[4.196:417](∅→∅),[4.196]→[4.196:417](∅→∅)
  − longest := ""

  − for k := 0; k < len(str)/2+1; k++ {

  − candidate := string(str[k])

  − for i := 1; true; i++ {

  − // avoid overrun or underrun

  − if (k-i < 0) || (k+i > len(str)-1) {

  − break

  − }

  − // two identical bytes
  [2.173]

  [4.417]
  + if str == "" {

  + return ""

  + }

  + var longest string

  + for k := 1; k < len(str)/2+1; k++ {

  + var candidate string

  + for i := 1; k-i > -1 && k+i < len(str); i++ {
• replacement in snippets/palindrome/palindrome.go at line 17
  [4.446]→[4.446:510](∅→∅)
  − candidate = string(str[k-i]) + candidate + string(str[k+i])
  [4.446]

  [4.510]
  + candidate = str[k-i : k+i+1]
• replacement in snippets/palindrome/palindrome.go at line 26
  [4.608]→[3.0:54](∅→∅)
  − if len(longest) > 1 {

  − return longest

  − }

  − return ""
  [4.608]

  [4.624]
  + return longest
• edit in snippets/palindrome/palindrome.go at line 32
  [2.264]

  [6.534]
  + if str == "" {

  + return ""

  + }