Leetcode-75. Sort Colors

前言：为了后续的实习面试，开始疯狂刷题，非常欢迎志同道合的朋友一起交流。因为时间比较紧张，目前的规划是先过一遍，写出能想到的最优算法，第二遍再考虑最优或者较优的方法。如有错误欢迎指正。博主首发优快云，mcf171专栏。

博客链接：mcf171的博客

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Given an array with n objects colored red, white or blue, sort them 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.

Note:
You are not suppose to use the library's sort function for this problem.

click to show follow up.

Follow up:
A rather straight forward solution is a two-pass algorithm using counting sort.
First, iterate the array counting number of 0's, 1's, and 2's, then overwrite array with total number of 0's, then 1's and followed by 2's.

Could you come up with an one-pass algorithm using only constant space?

本来想尝试使用遍历一遍的方法，但是没想到老是有一些边界点没考虑到。算了，还是简单一点先统计一遍。。 Your runtime beats 53.37% of java submissions.

public class Solution {
    public void sortColors(int[] nums) {
        int[] store = new int[3];

        for(int item : nums){
            store[item] ++;
        }

        for(int i = 0; i < store[0]; i ++) nums[i] = 0;
        for(int i = 0; i < store[1]; i ++) nums[i + store[0]] = 1;
        for(int i = 0; i < store[2]; i ++) nums[i+ store[0] + store[1]] = 2;
    }
}