75. Sort Colors

Given an array nums with n objects colored red, white, or blue, sort them in-place so that objects of the same color are adjacent, with the colors in the order red, white, and blue.

We will use the integers 0, 1, and 2 to represent the color red, white, and blue, respectively.

 

Example 1:

Input: nums = [2,0,2,1,1,0]
Output: [0,0,1,1,2,2]

Example 2:

Input: nums = [2,0,1]
Output: [0,1,2]

Example 3:

Input: nums = [0]
Output: [0]

Example 4:

Input: nums = [1]
Output: [1]

 

Constraints:

  • n == nums.length
  • 1 <= n <= 300
  • nums[i] is 0, 1, or 2.

 

Follow up:

  • Could you solve this problem without using the library's sort function?
  • Could you come up with a one-pass algorithm using only O(1) constant space?

Rust Solution

struct Solution;

impl Solution {
    fn sort_colors(nums: &mut Vec<i32>) {
        let n = nums.len();
        let mut l = 0;
        let mut r = n - 1;
        let mut i = 0;
        while i <= r {
            while nums[i] == 2 && i < r {
                nums.swap(i, r);
                r -= 1;
            }
            while nums[i] == 0 && i > l {
                nums.swap(i, l);
                l += 1;
            }
            i += 1;
        }
    }
}

#[test]
fn test() {
    let mut nums = vec![2, 0, 2, 1, 1, 0];
    let res = vec![0, 0, 1, 1, 2, 2];
    Solution::sort_colors(&mut nums);
    assert_eq!(nums, res);
}

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