LeetCode in Kotlin

75. Sort Colors

Medium

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 {
    fun sortColors(nums: IntArray) {
        var zeroes = 0
        var ones = 0
        for (i in nums.indices) {
            if (nums[i] == 0) {
                nums[zeroes++] = 0
            } else if (nums[i] == 1) {
                ones++
            }
        }
        for (j in zeroes until zeroes + ones) {
            nums[j] = 1
        }
        for (k in zeroes + ones until nums.size) {
            nums[k] = 2
        }
    }
}

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