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- 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?
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- class Solution {
- public void sortColors(int[] nums) {
- if(nums.length == 0 || nums.length == 1) return;
- int[] arr = new int [3];
-
- for(int i = 0; i< nums.length; i++){
-
- arr[nums[i]]++;
- }
- int count = 0;
- int i = 0;
- while(count != 3){
- while(arr[count] != 0) {
- arr[count]--;
- nums[i++] = count;
- }
- count++;
- }
-
- }
- }
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