颜色分类

public void sortColors(int[] nums){
    int zero = -1;
    int two = nums.length;

    for(int i = 0; i < two; ){
        if(nums[i] == 1){
            i ++;
        }else if(nums[i] == 2){
            two --;
            swap(nums,i,two);
        }else {  //nums[i] == 0
            zero ++;
            swap(nums,zero,i);
            i ++;
        }
    }
}

private void swap(int[] nums, int i, int j){
    int t = nums[i];
    nums[i] = nums[j];
    nums[j] = t;
}

https://leetcode-cn.com/problems/sort-colors/

来源LeetCode75号题目-颜色分类，具体解题要求，官网上详见。