Given an unsorted integer array nums, find the smallest missing positive integer.
Follow up: Could you implement an algorithm that runs in O(n) time and uses constant extra space.?
Example 1:
Input: nums = [1,2,0] Output: 3
Example 2:
Input: nums = [3,4,-1,1] Output: 2
Example 3:
Input: nums = [7,8,9,11,12] Output: 1
Constraints:
0 <= nums.length <= 300-231 <= nums[i] <= 231 - 1struct Solution;
impl Solution {
fn first_missing_positive(mut nums: Vec<i32>) -> i32 {
let n = nums.len();
for i in 0..n {
loop {
let j = nums[i] - 1;
if j >= 0 && j < n as i32 && nums[j as usize] != nums[i] {
nums.swap(i, j as usize);
} else {
break;
}
}
}
for i in 0..n {
if nums[i] != i as i32 + 1 {
return (i + 1) as i32;
}
}
(n + 1) as i32
}
}
#[test]
fn test() {
let nums = vec![1, 2, 0];
let res = 3;
assert_eq!(Solution::first_missing_positive(nums), res);
let nums = vec![3, 4, -1, 1];
let res = 2;
assert_eq!(Solution::first_missing_positive(nums), res);
let nums = vec![7, 8, 9, 11, 12];
let res = 1;
assert_eq!(Solution::first_missing_positive(nums), res);
}