rs: add «205. Isomorphic Strings»

Signed-off-by: Matej Focko <mfocko@redhat.com>

rs/isomorphic-strings.rs

@@ -0,0 +1,27 @@
+use std::collections::{HashMap, HashSet};
+
+impl Solution {
+    pub fn is_isomorphic(s: String, t: String) -> bool {
+        let mut projection: HashMap<char, char> = HashMap::new();
+        let mut used: HashSet<char> = HashSet::new();
+
+        for (l, r) in s.chars().zip(t.chars()) {
+            match projection.get(&l) {
+                Some(&expected_r) if expected_r != r => {
+                    return false;
+                }
+                None => {
+                    if used.contains(&r) {
+                        return false;
+                    }
+
+                    projection.insert(l, r);
+                    used.insert(r);
+                }
+                _ => { /* no-op */ }
+            }
+        }
+
+        true
+    }
+}