Given integer array nums, return the third maximum number in this array. If the third maximum does not exist, return the maximum number.
Example 1:
Input: nums = [3,2,1] Output: 1 Explanation: The third maximum is 1.
Example 2:
Input: nums = [1,2] Output: 2 Explanation: The third maximum does not exist, so the maximum (2) is returned instead.
Example 3:
Input: nums = [2,2,3,1] Output: 1 Explanation: Note that the third maximum here means the third maximum distinct number. Both numbers with value 2 are both considered as second maximum.
Constraints:
1 <= nums.length <= 104-231 <= nums[i] <= 231 - 1Follow up: Can you find an
O(n) solution?struct Solution;
use std::cmp::Ordering::*;
impl Solution {
fn third_max(nums: Vec<i32>) -> i32 {
let mut max1 = nums[0];
let mut m2: Option<i32> = None;
let mut m3: Option<i32> = None;
for x in nums {
match x.cmp(&max1) {
Greater => {
m3 = m2;
m2 = Some(max1);
max1 = x;
}
Less => {
if let Some(max2) = m2 {
match x.cmp(&max2) {
Greater => {
m3 = m2;
m2 = Some(x);
}
Less => {
if let Some(max3) = m3 {
if x > max3 {
m3 = Some(x);
}
} else {
m3 = Some(x);
}
}
Equal => {}
}
} else {
m2 = Some(x);
}
}
Equal => {}
}
}
if let Some(max3) = m3 {
max3
} else {
max1
}
}
}
#[test]
fn test() {
let nums = vec![3, 2, 1];
assert_eq!(Solution::third_max(nums), 1);
let nums = vec![1, 2];
assert_eq!(Solution::third_max(nums), 2);
let nums = vec![2, 2, 3, 1];
assert_eq!(Solution::third_max(nums), 1);
let nums = vec![1, 2, 2, 5, 3, 5];
assert_eq!(Solution::third_max(nums), 2);
}