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:
- You must do this in-place without making a copy of the array.
- Minimize the total number of operations.
Analysis
方法一：从尾向前遍历，如果是0移到尾后，而后的元素向前移位。
方法二：滚雪球法。
这题我轻视了，耗了不少时间。
Submission
public class MoveZeroes {
//方法一：从尾向前遍历，如果是0移到尾后，而后的元素向前移位
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：滚雪球法
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);
}
}