75. Sort Colors

[blueWind123731]

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.

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

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?

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.

[blueWind123731]

把所有的0移到左边，把所有的2移到右边，剩余的1即在中间。

var sortColors = function(nums) {
    let left = 0,right = nums.length-1;
    for(let i=0;i<=right;i++){
        while(nums[i]===2&&i<right){
            [nums[i],nums[right]]=[nums[right],nums[i]]
            right--
        }
        while(nums[i]===0&&i>left){
            [nums[left],nums[i]]=[nums[i],nums[left]]
            left++
        }
    }
};