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89 lines
2.1 KiB
Rust
89 lines
2.1 KiB
Rust
// Copyright 2022 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// ANCHOR: luhn
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pub fn luhn(cc_number: &str) -> bool {
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// ANCHOR_END: luhn
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let mut digits_seen = 0;
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let mut sum = 0;
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for (i, ch) in cc_number.chars().rev().filter(|&ch| ch != ' ').enumerate() {
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match ch.to_digit(10) {
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Some(d) => {
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sum += if i % 2 == 1 {
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let dd = d * 2;
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dd / 10 + dd % 10
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} else {
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d
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};
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digits_seen += 1;
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}
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None => return false,
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}
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}
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if digits_seen < 2 {
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return false;
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}
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sum % 10 == 0
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}
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fn main() {
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let cc_number = "1234 5678 1234 5670";
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println!(
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"Is {} a valid credit card number? {}",
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cc_number,
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if luhn(cc_number) { "yes" } else { "no" }
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);
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}
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// ANCHOR: unit-tests
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#[test]
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fn test_non_digit_cc_number() {
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assert!(!luhn("foo"));
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}
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#[test]
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fn test_empty_cc_number() {
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assert!(!luhn(""));
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assert!(!luhn(" "));
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assert!(!luhn(" "));
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assert!(!luhn(" "));
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}
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#[test]
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fn test_single_digit_cc_number() {
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assert!(!luhn("0"));
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}
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#[test]
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fn test_two_digit_cc_number() {
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assert!(luhn(" 0 0 "));
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}
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#[test]
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fn test_valid_cc_number() {
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assert!(luhn("4263 9826 4026 9299"));
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assert!(luhn("4539 3195 0343 6467"));
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assert!(luhn("7992 7398 713"));
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}
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#[test]
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fn test_invalid_cc_number() {
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assert!(!luhn("4223 9826 4026 9299"));
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assert!(!luhn("4539 3195 0343 6476"));
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assert!(!luhn("8273 1232 7352 0569"));
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}
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// ANCHOR_END: unit-tests
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