rs: add «997. Find the Town Judge»

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

rs/find-the-town-judge.rs

@@ -0,0 +1,31 @@
+impl Solution {
+    pub fn find_judge(n: i32, trust: Vec<Vec<i32>>) -> i32 {
+        let mut trusts: Vec<i32> = vec![0; n as usize];
+        let mut trusted_by: Vec<i32> = vec![0; n as usize];
+
+        // set the counters
+        for vertices in &trust {
+            let u = vertices[0] as usize;
+            let v = vertices[1] as usize;
+
+            trusts[u - 1] += 1;
+            trusted_by[v - 1] += 1;
+        }
+
+        // find the judge
+        let mut judge = -1;
+        for i in 0..n as usize {
+            if trusts[i] != 0 || trusted_by[i] != n - 1 {
+                continue;
+            }
+
+            if judge != -1 {
+                return -1;
+            }
+
+            judge = i as i32 + 1;
+        }
+
+        judge
+    }
+}