Add solution sheet7

aufgaben/sheet7/sol2/iters.rs

@@ -0,0 +1,93 @@
+fn factorial(x: u64) -> u64 {
+    (1..x + 1).product()
+}
+
+#[test]
+fn test_factorial() {
+    assert_eq!(factorial(1), 1);
+    assert_eq!(factorial(2), 2);
+    assert_eq!(factorial(3), 6);
+    assert_eq!(factorial(15), 1_307_674_368_000);
+}
+
+fn is_palindrome(word: &str) -> bool {
+    word.chars()
+        .zip(word.chars().rev())
+        // This is just an optional optimization
+        .take(word.len() / 2)
+        .all(|(a, b)| a == b)
+}
+
+#[test]
+fn test_is_palindrome() {
+    assert!(is_palindrome("bob"));
+    assert!(is_palindrome("anna"));
+    assert!(is_palindrome("lagerregal"));
+
+    assert!(!is_palindrome("peter"));
+}
+
+fn greatest_subsequencial_sum(arr: &[i64]) -> &[i64] {
+    // all possible window lengths
+    (1..arr.len() + 1)
+        // iterate over all possible windows
+        .flat_map(|len| arr.windows(len))
+        // add the empty slice in case all numbers are negative
+        .chain(std::iter::once(&arr[0..0]))
+        // we want to select the window which sum is the greatest
+        .max_by_key(|win| win.iter().sum::<i64>())
+        // we know our iterator has at least one element
+        .unwrap()
+}
+
+#[test]
+fn test_greatest_subsequencial_sum() {
+    let a = [1, 2, 39, 34, 20, -20, -16, 35, 0];
+    assert_eq!(greatest_subsequencial_sum(&a), &a[0..5]);
+
+    let b = [-3, -9, -8, -34];
+    assert_eq!(greatest_subsequencial_sum(&b), &[]);
+}
+
+fn rot13(s: &str) -> String {
+    s.chars().map(|c| {
+        match c {
+            'a' ... 'm' | 'A' ... 'M' => (c as u8 + 13) as char,
+            'n' ... 'z' | 'N' ... 'Z' => (c as u8 - 13) as char,
+            _ => c
+        }
+    }).collect()
+}
+
+#[test]
+fn test_rot13() {
+    assert_eq!(rot13("hello"), "uryyb");
+    assert_eq!(rot13("uryyb"), "hello");
+
+    assert_eq!(
+        rot13("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"),
+        "NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm"
+    );
+
+    assert_eq!(rot13("peter"), "crgre");
+}
+
+fn used_chars_count<S: AsRef<str>>(words: &[S]) -> usize {
+    use std::collections::HashSet;
+
+    words.iter()
+        .flat_map(|w| w.as_ref().chars())
+        .filter(|c| !c.is_whitespace())
+        .collect::<HashSet<_>>()
+        .len()
+}
+
+#[test]
+fn test_used_letters() {
+    assert_eq!(used_chars_count(&["hi", "ih gitt"]), 4);
+    assert_eq!(used_chars_count(&["peter"]), 4);
+    assert_eq!(used_chars_count(&["p e t e r", "barbara"]), 6);
+}
+
+fn main() {
+}