An exercise gives me football matches, with teams and their scores (like: "England,France,4,2"), and I have to insert the teams in a hashmap with its goals scored and conceded. The key is the name of the team and I pass the goals scored and conceded as a struct.
The exercise then gives me another string with a team already in the hashmap ("England,Spain,1,3") and I have to update the hashmap on the England key, adding the goals from that match. How can I do that?
My code (playground):
// hashmaps3.rs
// A list of scores (one per line) of a soccer 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 the 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 `rustlings hint hashmaps3` or use the `hint` watch subcommand for a hint.
// 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> {
// The name of the team is the key and its associated struct 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();
let team_1 = Team {
name: team_1_name.clone(),
goals_scored: team_1_score,
goals_conceded: team_2_score,
};
let team_2 = Team {
name: team_2_name.clone(),
goals_scored: team_2_score,
goals_conceded: team_1_score,
};
let team1 = scores.entry(team_1_name).or_insert(team_1);
let team2 = scores.entry(team_2_name).or_insert(team_2);
team1.goals_scored += team_1_score;
team1.goals_conceded += team_2_score;
team2.goals_scored += team_2_score;
team2.goals_conceded += team_1_score;
}
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);
}
}
Error:
error[E0499]: cannot borrow `scores` as mutable more than once at a time
--> src/lib.rs:49:21
|
48 | let team1 = scores.entry(team_1_name).or_insert(team_1);
| ------------------------- first mutable borrow occurs here
49 | let team2 = scores.entry(team_2_name).or_insert(team_2);
| ^^^^^^^^^^^^^^^^^^^^^^^^^ second mutable borrow occurs here
50 | team1.goals_scored += team_1_score;
| ---------------------------------- first borrow later used here
I think I understand the error, so I have tried using
let team1 = &mut scores.entry.... That is spitting some weird errors. So I am lost here, any help would be much appreciated.
