feat: Add hashmap3 exercise.

exercises/collections/hashmap3.rs

@@ -0,0 +1,88 @@
+// hashmap3.rs
+
+// A list of scores (one per line) of a match is given. Each line is
+// of the form :
+// <team_1_name>,<team_2_name>,<team_1_goals>,<team_2_goals>
+// Example: England,France,4,2 (England scored 4 goals, France 2).
+
+// You have to build a scores table containing name of the team, goals
+// the team scored, and goals the team conceded. One approach to build
+// the scores table is to use a Hashmap. The solution is partially
+// written to use a Hashmap, complete it to pass the test.
+
+// Make me pass the tests!
+
+// Execute the command `rustlings hint hashmap3` if you need
+// hints.
+
+// I AM NOT DONE
+
+use std::collections::HashMap;
+
+// A structure to store team name and its goal details.
+struct Team {
+    name: String,
+    goals_scored: u8,
+    goals_conceded: u8,
+}
+
+fn build_scores_table(results: String) -> HashMap<String, Team> {
+    // name of the team is the key and corresponding team is the value.
+    let mut scores: HashMap<String, Team> = HashMap::new();
+
+    for r in results.lines() {
+        let v: Vec<&str> = r.split(',').collect();
+        let team_1_name = v[0].to_string();
+        let team_1_score: u8 = v[2].parse().unwrap();
+        let team_2_name = v[1].to_string();
+        let team_2_score: u8 = v[3].parse().unwrap();
+        // TODO: Populate scores table with details extracted from the
+        // current line. Keep in mind that goals scored by team_1,
+        // will be number of goals conceded by the team_2, similarly
+        // goals scored by team_2 will be number of goals conceded by
+        // team_1.
+    }
+    scores
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn get_results() -> String {
+        let results = "".to_string()
+            + "England,France,4,2\n"
+            + "France,Italy,3,1\n"
+            + "Poland,Spain,2,0\n"
+            + "Germany,England,2,1\n";
+        results
+    }
+
+    #[test]
+    fn build_scores() {
+        let scores = build_scores_table(get_results());
+
+        let mut keys: Vec<&String> = scores.keys().collect();
+        keys.sort();
+        assert_eq!(
+            keys,
+            vec!["England", "France", "Germany", "Italy", "Poland", "Spain"]
+        );
+    }
+
+    #[test]
+    fn validate_team_score_1() {
+        let scores = build_scores_table(get_results());
+        let team = scores.get("England").unwrap();
+        assert_eq!(team.goals_scored, 5);
+        assert_eq!(team.goals_conceded, 4);
+    }
+
+    #[test]
+    fn validate_team_score_2() {
+        let scores = build_scores_table(get_results());
+        let team = scores.get("Spain").unwrap();
+        assert_eq!(team.goals_scored, 0);
+        assert_eq!(team.goals_conceded, 2);
+    }
+}

info.toml

@@ -417,6 +417,17 @@ Use the `entry()` and `or_insert()` methods of `HashMap` to achieve this.
 Learn more at https://doc.rust-lang.org/stable/book/ch08-03-hash-maps.html#only-inserting-a-value-if-the-key-has-no-value
 """
 
+[[exercises]]
+name = "hashmap3"
+path = "exercises/collections/hashmap3.rs"
+mode = "test"
+hint = """
+Hint 1: Use the `entry()` and `or_insert()` methods of `HashMap` to insert entries corresponding to each team in the scores table.
+Learn more at https://doc.rust-lang.org/stable/book/ch08-03-hash-maps.html#only-inserting-a-value-if-the-key-has-no-value
+Hint 2: If there is already an entry for a given key, the value returned by `entry()` can be updated based on the existing value.
+Learn more at https://doc.rust-lang.org/book/ch08-03-hash-maps.html#updating-a-value-based-on-the-old-value
+"""
+
 # STRINGS
 
 [[exercises]]