Shortest word distance

#[test]
fn test_adjacent() {
    let start = std::time::Instant::now();
    let val = Solution::shortest_distance(vec!["a".to_string(), "b".to_string()], "a".to_string(), "b".to_string());
    let expected = 1;
    log_result!(val == expected, "test_adjacent", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn test_example1() {
    let start = std::time::Instant::now();
    let val = Solution::shortest_distance(vec!["practice".to_string(), "makes".to_string(), "perfect".to_string(), "coding".to_string(), "makes".to_string()], "coding".to_string(), "practice".to_string());
    let expected = 3;
    log_result!(val == expected, "test_example1", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn test_example2() {
    let start = std::time::Instant::now();
    let val = Solution::shortest_distance(vec!["practice".to_string(), "makes".to_string(), "perfect".to_string(), "coding".to_string(), "makes".to_string()], "makes".to_string(), "coding".to_string());
    let expected = 1;
    log_result!(val == expected, "test_example2", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn test_far_apart() {
    let start = std::time::Instant::now();
    let val = Solution::shortest_distance(vec!["a".to_string(), "c".to_string(), "c".to_string(), "c".to_string(), "b".to_string()], "a".to_string(), "b".to_string());
    let expected = 4;
    log_result!(val == expected, "test_far_apart", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn test_multiple_occurrences() {
    let start = std::time::Instant::now();
    let val = Solution::shortest_distance(vec!["a".to_string(), "b".to_string(), "c".to_string(), "a".to_string(), "b".to_string()], "a".to_string(), "b".to_string());
    let expected = 1;
    log_result!(val == expected, "test_multiple_occurrences", start, &expected, &val);
    assert_eq!(val, expected);
}