LeetCode - Easy - 283. Move Zeroes

Topic

• Array
• Two Pointers

Description

https://leetcode.com/problems/move-zeroes/

Given an array nums, write a function to move all 0's to the end of it while maintaining the relative order of the non-zero elements.

Example:

Input: [0,1,0,3,12]
Output: [1,3,12,0,0]

Note:

1. You must do this in-place without making a copy of the array.
2. Minimize the total number of operations.

Analysis

方法一：從尾向前遍歷，如果是0移到尾後，而後的元素向前移位。

方法二：滾雪球法。

---

這題我輕視了，耗了不少時間。

Submission

public class MoveZeroes {

	//方法一：從尾向前遍歷，如果是0移到尾後，而後的元素向前移位
	public void moveZeroes1(int[] nums) {
		if (nums == null)
			return;

		int end = nums.length - 1;
		for (int i = nums.length - 1; i > -1; i--) {
			if (nums[i] == 0) {
				for (int j = i + 1; j <= end; j++)
					nums[j - 1] = nums[j];
				nums[end--] = 0;
			}
		}
	}

	//方法二：滾雪球法
	public void moveZeroes2(int[] nums) {
		if (nums == null)
			return;

		int cur = 0;

		for (int i = 0; i < nums.length; ++i) {
			if (nums[i] != 0) {
				int temp = nums[cur];
				nums[cur++] = nums[i];
				nums[i] = temp;
			}
		}
	}
}

Test

import static org.junit.Assert.*;
import org.junit.Test;

public class MoveZeroesTest {

	@Test
	public void test1() {
		MoveZeroes obj = new MoveZeroes();

		int[] original = {0, 1, 0, 3, 12};
		int[] expected = {1, 3, 12, 0, 0};
		obj.moveZeroes1(original);
		assertArrayEquals(expected, original);
		
		original = new int[]{1};
		expected = new int[]{1};
		obj.moveZeroes1(original);
		assertArrayEquals(expected, original);
		
		original = new int[]{1, 0};
		expected = new int[]{1, 0};
		obj.moveZeroes1(original);
		assertArrayEquals(expected, original);
		
		original = new int[]{2, 1};
		expected = new int[]{2, 1};
		obj.moveZeroes1(original);
		assertArrayEquals(expected, original);
		
		original = new int[]{0, 0, 1};
		expected = new int[]{1, 0, 0};
		obj.moveZeroes1(original);
		assertArrayEquals(expected, original);

	}
	
	@Test
	public void test2() {
		MoveZeroes obj = new MoveZeroes();
		
		int[] original = {0, 1, 0, 3, 12};
		int[] expected = {1, 3, 12, 0, 0};
		obj.moveZeroes2(original);
		assertArrayEquals(expected, original);
		
		original = new int[]{1};
		expected = new int[]{1};
		obj.moveZeroes2(original);
		assertArrayEquals(expected, original);
		
		original = new int[]{1, 0};
		expected = new int[]{1, 0};
		obj.moveZeroes2(original);
		assertArrayEquals(expected, original);
		
		original = new int[]{2, 1};
		expected = new int[]{2, 1};
		obj.moveZeroes2(original);
		assertArrayEquals(expected, original);
		
		original = new int[]{0, 0, 1};
		expected = new int[]{1, 0, 0};
		obj.moveZeroes2(original);
		assertArrayEquals(expected, original);
		
	}
}