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SortColors.java
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53 lines (52 loc) · 1.72 KB
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package com.yangchd.leetcode.medium;
/**
* @author yangchd 2018/11/4
*
* 75.Sort Colors
* Given an array with n objects colored red, white or blue, sort them in-place 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.
*
* Example:
* Input: [2,0,2,1,1,0]
* Output: [0,0,1,1,2,2]
*
* 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 a one-pass algorithm using only constant space?
*
*/
public class SortColors {
/**
* 这种有确定种类的排序，可以直接采用计数赋值的方法
*/
class Solution {
public void sortColors(int[] nums) {
int red = 0;
int white = 0;
int blue = 0;
for (int num : nums) {
if (num == 0) {
red++;
}
if (num == 1) {
white++;
}
if (num == 2) {
blue++;
}
}
for (int i = 0; i < nums.length; i++) {
if (i < red) {
nums[i] = 0;
} else if (i >= red && i < red + white) {
nums[i] = 1;
} else if (i >= red + white && i < red + white + blue) {
nums[i] = 2;
}
}
}
}
}