diff --git a/src/lib.rs b/src/lib.rs
index 12330e8..066b33b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,4 +1,5 @@
 pub mod lib {
+    use std::collections::HashSet;
     use std::fs;
     use std::io::Write;
 
@@ -9,10 +10,10 @@ pub mod lib {
     const ERR_CANNOT_BEGIN_FILE: &str = "Could not begin file in zip archive";
 
     pub struct IDs<'a> {
-        pub blue: Vec<&'a str>,
-        pub red: Vec<&'a str>,
-        pub violet: Vec<&'a str>,
-        pub unknown: Vec<&'a str>,
+        pub blue: HashSet<&'a str>,
+        pub red: HashSet<&'a str>,
+        pub violet: HashSet<&'a str>,
+        pub unknown: HashSet<&'a str>,
     }
 
     pub struct Descriptors<T: Write> {
diff --git a/src/main.rs b/src/main.rs
index 38e7047..fec7a3e 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,4 @@
+use std::collections::HashSet;
 use std::io::{BufRead, BufReader};
 use std::{fs, str};
 
@@ -55,10 +56,10 @@ fn divide_body_by_coalition(body: &Vec<String>) -> lib::BodiesByCoalition {
     let mut continued = false;
     let mut line_type = LineType::Unknown;
     let mut coalitions = lib::IDs {
-        blue: Vec::new(),
-        red: Vec::new(),
-        violet: Vec::new(),
-        unknown: Vec::new(),
+        blue: HashSet::new(),
+        red: HashSet::new(),
+        violet: HashSet::new(),
+        unknown: HashSet::new(),
     };
     for line in body {
         let result = process_line(continued, &mut coalitions, line, line_type);
@@ -120,13 +121,13 @@ fn get_id_from_line(line: &str) -> &str {
 fn assign_id_to_coalitions<'a>(coalitions: &mut lib::IDs<'a>, line: &'a str, id: &'a str) {
     if line.contains("Color=") {
         if line.contains("Color=Blue") {
-            coalitions.blue.push(id);
+            coalitions.blue.insert(id);
         } else if line.contains("Color=Red") {
-            coalitions.red.push(id);
+            coalitions.red.insert(id);
         } else if line.contains("Color=Violet") {
-            coalitions.violet.push(id);
+            coalitions.violet.insert(id);
         } else {
-            coalitions.unknown.push(id);
+            coalitions.unknown.insert(id);
         }
     }
 }