Sort Colors

Sort Colors

问题：

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.

思路：

　　双指针看数组，左指针代表0的位置，右指针代表2的位置

我的代码：

public class Solution {
    public void sortColors(int[] A) {
        if(A == null || A.length == 0)  return;
        int len = A.length;
        int zeroIndex = 0, curIndex = 0;
        int twoIndex = len - 1;
        while(curIndex <= twoIndex)
        {
            if(A[curIndex] == 1)
            {
                curIndex++;
            }
            else if(A[curIndex] == 0)
            {
                int change = A[zeroIndex];
                A[zeroIndex] = A[curIndex];
                A[curIndex] = change;
                curIndex++;
                zeroIndex++;
            }
            else
            {
                int change = A[twoIndex];
                A[twoIndex] = A[curIndex];
                A[curIndex] = change;
                twoIndex--;
            }
        }
        return;
    }
}

他人代码：

public class Solution {
    public void sortColors(int[] a) {
        if(a == null || a.length <= 1)
            return;
        
        int pl = 0;
        int pr = a.length - 1;
        int i = 0;
        while(i <= pr){
            if(a[i] == 0){
                swap(a, pl, i);
                pl++;
                i++;
            }else if(a[i] == 1){
                i++;
            }else{
                swap(a, pr, i);
                pr--;
            }
        }
    }
    
    private void swap(int[] a, int i, int j){
        int tmp = a[i];
        a[i] = a[j];
        a[j] = tmp;
    }
}

学习之处：

• 代码思路一致，里面数值交换，用了两次，应该封装起来更好。