rs: add «2864. Maximum Odd Binary Number»

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

rs/maximum-odd-binary-number.rs

@@ -0,0 +1,21 @@
+use std::cmp;
+
+impl Solution {
+    pub fn maximum_odd_binary_number(s: String) -> String {
+        let mut bits: Vec<char> = s.chars().collect();
+
+        // sort in reverse order, all ones are at the beginning
+        bits.sort_unstable_by_key(|&x| cmp::Reverse(x));
+
+        // find the last one
+        let i = bits.iter().rposition(|&x| x == '1').unwrap();
+
+        // and swap with the last zero to obtain odd integer
+        let last_index = bits.len() - 1;
+        if i < last_index {
+            bits.swap(i, last_index);
+        }
+
+        bits.into_iter().collect()
+    }
+}