LeetCode in Php

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]

Example 3:

Input: nums = [0]

Output: [0]

Example 4:

Input: nums = [1]

Output: [1]

Constraints:

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

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

Solution

class Solution {
    /**
     * @param Integer[] $nums
     * @return NULL
     */
    public function sortColors(&$nums) {
        $zeroes = 0;
        $ones = 0;
        for ($i = 0; $i < count($nums); $i++) {
            if ($nums[$i] == 0) {
                $nums[$zeroes++] = 0;
            } elseif ($nums[$i] == 1) {
                $ones++;
            }
        }
        for ($j = $zeroes; $j < $zeroes + $ones; $j++) {
            $nums[$j] = 1;
        }
        for ($k = $zeroes + $ones; $k < count($nums); $k++) {
            $nums[$k] = 2;
        }
    }
}