75. Sort Colors (Leetcode || Medium || Java)

Given an array nums 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.

We will use the integers 0, 1, and 2 to represent the color red, white, and blue, respectively.

You must solve this problem without using the library’s sort function.

Example 1:

Input: nums = [2,0,2,1,1,0]
Output: [0,0,1,1,2,2]

Example 2:

Input: nums = [2,0,1]
Output: [0,1,2]

Constraints:

• n == nums.length
• 1 <= n <= 300
• nums[i] is either 0, 1, or 2.

Follow up: Could you come up with a one-pass algorithm using only constant extra space?

SOLUTION:

class Solution {
public void sortColors(int[] nums) {
int[] temp = new int[nums.length];//Create a temporary array
int count = 0;

for(int i = 0; i < nums.length; i++){//run loop, if element is 0 add in temp
if(nums[i] == 0){
temp[count] = nums[i];
count++;
}
}
for(int i = 0; i < nums.length; i++){//As all zeroes are added above,now run loop for adding 1
if(nums[i] == 1){
temp[count] = nums[i];
count++;
}
}
for(int i = 0; i < nums.length; i++){//Now both 0 and 1 are sorted in the temp array, now sort 2
if(nums[i] == 2){
temp[count] = nums[i];
count++;
}
}
for(int j = 0; j < nums.length; j++){//Add all the elements of temp to original array
nums[j] = temp[j];
}

}