Day 2 Afternoon Exercises

Luhn Algorithm

(back to exercise)

  1. // Copyright 2022 Google LLC
  2. //
  3. // Licensed under the Apache License, Version 2.0 (the "License");
  4. // you may not use this file except in compliance with the License.
  5. // You may obtain a copy of the License at
  6. //
  7. //      http://www.apache.org/licenses/LICENSE-2.0
  8. //
  9. // Unless required by applicable law or agreed to in writing, software
  10. // distributed under the License is distributed on an "AS IS" BASIS,
  11. // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12. // See the License for the specific language governing permissions and
  13. // limitations under the License.
  15. // ANCHOR: luhn
  16. pub fn luhn(cc_number: &str) -> bool {
  17.     // ANCHOR_END: luhn
  18.     let mut digits_seen = 0;
  19.     let mut sum = 0;
  20.     for (i, ch) in cc_number.chars().rev().filter(|&ch| ch != ' ').enumerate() {
  21.         match ch.to_digit(10) {
  22.             Some(d) => {
  23.                 sum += if i % 2 == 1 {
  24.                     let dd = d * 2;
  25.                     dd / 10 + dd % 10
  26.                 } else {
  27.                     d
  28.                 };
  29.                 digits_seen += 1;
  30.             }
  31.             None => return false,
  32.         }
  33.     }
  35.     if digits_seen < 2 {
  36.         return false;
  37.     }
  39.     sum % 10 == 0
  40. }
  42. fn main() {
  43.     let cc_number = "1234 5678 1234 5670";
  44.     println!(
  45.         "Is {} a valid credit card number? {}",
  46.         cc_number,
  47.         if luhn(cc_number) { "yes" } else { "no" }
  48.     );
  49. }
  51. // ANCHOR: unit-tests
  52. #[test]
  53. fn test_non_digit_cc_number() {
  54.     assert!(!luhn("foo"));
  55. }
  57. #[test]
  58. fn test_empty_cc_number() {
  59.     assert!(!luhn(""));
  60.     assert!(!luhn(" "));
  61.     assert!(!luhn("  "));
  62.     assert!(!luhn("    "));
  63. }
  65. #[test]
  66. fn test_single_digit_cc_number() {
  67.     assert!(!luhn("0"));
  68. }
  70. #[test]
  71. fn test_two_digit_cc_number() {
  72.     assert!(luhn(" 0 0 "));
  73. }
  75. #[test]
  76. fn test_valid_cc_number() {
  77.     assert!(luhn("4263 9826 4026 9299"));
  78.     assert!(luhn("4539 3195 0343 6467"));
  79.     assert!(luhn("7992 7398 713"));
  80. }
  82. #[test]
  83. fn test_invalid_cc_number() {
  84.     assert!(!luhn("4223 9826 4026 9299"));
  85.     assert!(!luhn("4539 3195 0343 6476"));
  86.     assert!(!luhn("8273 1232 7352 0569"));
  87. }
  88. // ANCHOR_END: unit-tests

Strings and Iterators

(back to exercise)

  1. // Copyright 2022 Google LLC
  2. //
  3. // Licensed under the Apache License, Version 2.0 (the "License");
  4. // you may not use this file except in compliance with the License.
  5. // You may obtain a copy of the License at
  6. //
  7. //      http://www.apache.org/licenses/LICENSE-2.0
  8. //
  9. // Unless required by applicable law or agreed to in writing, software
  10. // distributed under the License is distributed on an "AS IS" BASIS,
  11. // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12. // See the License for the specific language governing permissions and
  13. // limitations under the License.
  15. // ANCHOR: prefix_matches
  16. pub fn prefix_matches(prefix: &str, request_path: &str) -> bool {
  17.     // ANCHOR_END: prefix_matches
  18.     let prefixes = prefix.split('/');
  19.     let request_paths = request_path
  20.         .split('/')
  21.         .map(|p| Some(p))
  22.         .chain(std::iter::once(None));
  24.     for (prefix, request_path) in prefixes.zip(request_paths) {
  25.         match request_path {
  26.             Some(request_path) => {
  27.                 if (prefix != "*") && (prefix != request_path) {
  28.                     return false;
  29.                 }
  30.             }
  31.             None => return false,
  32.         }
  33.     }
  34.     true
  35. }
  37. // ANCHOR: unit-tests
  38. #[test]
  39. fn test_matches_without_wildcard() {
  40.     assert!(prefix_matches("/v1/publishers", "/v1/publishers"));
  41.     assert!(prefix_matches("/v1/publishers", "/v1/publishers/abc-123"));
  42.     assert!(prefix_matches("/v1/publishers", "/v1/publishers/abc/books"));
  44.     assert!(!prefix_matches("/v1/publishers", "/v1"));
  45.     assert!(!prefix_matches("/v1/publishers", "/v1/publishersBooks"));
  46.     assert!(!prefix_matches("/v1/publishers", "/v1/parent/publishers"));
  47. }
  49. #[test]
  50. fn test_matches_with_wildcard() {
  51.     assert!(prefix_matches(
  52.         "/v1/publishers/*/books",
  53.         "/v1/publishers/foo/books"
  54.     ));
  55.     assert!(prefix_matches(
  56.         "/v1/publishers/*/books",
  57.         "/v1/publishers/bar/books"
  58.     ));
  59.     assert!(prefix_matches(
  60.         "/v1/publishers/*/books",
  61.         "/v1/publishers/foo/books/book1"
  62.     ));
  64.     assert!(!prefix_matches("/v1/publishers/*/books", "/v1/publishers"));
  65.     assert!(!prefix_matches(
  66.         "/v1/publishers/*/books",
  67.         "/v1/publishers/foo/booksByAuthor"
  68.     ));
  69. }
  70. // ANCHOR_END: unit-tests
  72. fn main() {}