[leetcode]75. Sort Colors(Java)

最新推荐文章于 2022-05-06 15:37:25 发布

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本文介绍了一种解决三色排序问题的有效算法，该算法通过桶排序实现，将红色、白色和蓝色三种颜色的对象按顺序排列。算法的时间复杂度为O(n)，但需要额外的O(n)空间。

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https://leetcode.com/problems/sort-colors/#/description

Given an array with n objects colored red, white or blue, sort them 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.

click to show follow up.

package go.jacob.day629;

public class Demo2 {
	/*
	 * 桶排序 Runtime: 0 ms.Your runtime beats 61.03 % of java submissions.
	 * 需要申请O(n)额外空间。 time：O(n).
	 */
	public void sortColors(int[] nums) {
		int[] count = new int[3];
		for (int i = 0; i < nums.length; i++) {
			if (nums[i] == 0)
				count[0]++;
			else if (nums[i] == 1)
				count[1]++;
			else
				count[2]++;
		}
		int index = 0;
		for (int i = 0; i < count[0]; i++) {
			nums[index++] = 0;
		}
		for (int i = 0; i < count[1]; i++) {
			nums[index++] = 1;
		}
		for (int i = 0; i < count[2]; i++) {
			nums[index++] = 2;
		}

	}
}