LeetCode 75（Sort Colors）Java

原题：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.

给定一个代表颜色的一维数组，其中用0代表红色，1代表白色，2代表蓝色。需要将相同的颜色放在一起，让他们相邻。

思路：这道题相当于对含有重复元素的数组进行排序，我代码中采用了归并排序的算法：

代码：

/*
Author:Jassy
Time:2016/11/30
Number:LeetCode 75
Resource:https://leetcode.com/problems/sort-colors/
Result:AC
Conclusion:MergeSort
*/
public class Solution {
    public void sortColors(int[] nums) {
        mergeSortColor(nums,0,nums.length-1);
    }
    
    void mergeSortColor(int[] nums,int left,int right){
        int mid=(left+right)/2;
        if(left==right){
            return;
        }else{
            mergeSortColor(nums,left,mid);
            mergeSortColor(nums,mid+1,right);
            merge(nums,left,mid,right);
        }
    }
    
    void merge(int[] nums,int left,int mid,int right){
        int[] leftSide=new int[mid-left+1];
        for(int i=left;i<=mid;i++){
            leftSide[i-left]=nums[i];
        }
        
        int[] rightSide=new int[right-mid];
        for(int i=mid;i<right;i++){
            rightSide[i-mid]=nums[i+1];
        }
        
        int leftCount=0;
        int rightCount=0;
        for(int i=left;i<=right;i++){
            if(leftCount<leftSide.length && rightCount<rightSide.length){
                if(leftSide[leftCount]<=rightSide[rightCount]){
                    nums[i]=leftSide[leftCount++];
                }else{
                    nums[i]=rightSide[rightCount++];
                }
            }else if(leftCount==leftSide.length){
                nums[i]=rightSide[rightCount++];
            }else{
                nums[i]=leftSide[leftCount++];
            }
        }
    }
}