leetcode解题方案--075--Sort Colors

题目

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.

分析

计数排序

先便利一遍每个颜色分别有几个，

然后再遍历一遍赋值

还有一种思路是设置两个指针把三种颜色分离开，指针不断向左向右移动

class Solution {
public static void sortColors(int[] num) {
int num0 = 0;
int num1 = 0;
int num2 = 0;
for (int i = 0; i<num.length; i++) {
if (num[i] == 0) {
num0++;
} else if (num[i] == 1) {
num1++;
} else if (num[i] == 2) {
num2++;
}
}
for (int i = 0; i<num0; i++) {
num[i] = 0;
}
for (int i = 0; i<num1; i++) {
num[num0+i] = 1;
}
for (int i = 0; i<num2; i++) {
num[num0+num1+i] = 2;
}
//        System.out.print(Arrays.toString(num));
}
}