rs: add “1657. Determine if Two Strings Are Close”

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

rs/determine-if-two-strings-are-close.rs

@@ -0,0 +1,39 @@
+use std::convert::TryFrom;
+
+impl Solution {
+    fn freqs(word: &str) -> Vec<usize> {
+        let mut f = vec![0; 26];
+
+        let zero = u8::try_from('a').unwrap();
+        for c in word.chars().filter_map(|c| match u8::try_from(c) {
+            Ok(val) => Some(val),
+            _ => None,
+        }) {
+            f[(c - zero) as usize] += 1;
+        }
+
+        f
+    }
+
+    fn mask(f: &[usize]) -> i32 {
+        let mut m = 0;
+
+        for c in f {
+            m = (m << 1) | if *c > 0 { 1 } else { 0 };
+        }
+
+        m
+    }
+
+    pub fn close_strings(word1: String, word2: String) -> bool {
+        let mut f1 = Solution::freqs(&word1);
+        let m1 = Solution::mask(&f1);
+        f1.sort();
+
+        let mut f2 = Solution::freqs(&word2);
+        let m2 = Solution::mask(&f2);
+        f2.sort();
+
+        m1 == m2 && f1 == f2
+    }
+}