Find center of star graph

#[test]
fn t1() {
    let start = std::time::Instant::now();
    let val = Solution::find_center(vec![vec![1, 2], vec![2, 3], vec![4, 2]]);
    let expected = 2;
    log_result!(val == expected, "t1", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t2() {
    let start = std::time::Instant::now();
    let val = Solution::find_center(vec![vec![1, 2], vec![5, 1], vec![1, 3], vec![1, 4]]);
    let expected = 1;
    log_result!(val == expected, "t2", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t3() {
    let start = std::time::Instant::now();
    let val = Solution::find_center(vec![vec![3, 1], vec![3, 2]]);
    let expected = 3;
    log_result!(val == expected, "t3", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t4() {
    let start = std::time::Instant::now();
    let val = Solution::find_center(vec![vec![2, 1], vec![2, 3], vec![2, 4]]);
    let expected = 2;
    log_result!(val == expected, "t4", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t5() {
    let start = std::time::Instant::now();
    let val = Solution::find_center(vec![vec![5, 4], vec![5, 3], vec![5, 2], vec![5, 1]]);
    let expected = 5;
    log_result!(val == expected, "t5", start, &expected, &val);
    assert_eq!(val, expected);
}