rs: add «506. Relative Ranks»

Signed-off-by: Matej Focko <me@mfocko.xyz>

rs/relative-ranks.rs

@@ -0,0 +1,30 @@
+use std::collections::BinaryHeap;
+
+impl Solution {
+    fn pos_to_string(pos: usize) -> String {
+        match pos {
+            0 => String::from("Gold Medal"),
+            1 => String::from("Silver Medal"),
+            2 => String::from("Bronze Medal"),
+            _ => format!("{}", pos + 1),
+        }
+    }
+
+    pub fn find_relative_ranks(score: Vec<i32>) -> Vec<String> {
+        let mut heap = BinaryHeap::new();
+
+        for (i, s) in score.into_iter().enumerate() {
+            heap.push((s, i));
+        }
+
+        let mut ranks = vec![String::new(); heap.len()];
+
+        let mut i = 0;
+        while let Some((_, idx)) = heap.pop() {
+            ranks[idx] = Self::pos_to_string(i);
+            i += 1;
+        }
+
+        ranks
+    }
+}