LeetCode_283. Move Zeroes

 

283. Move Zeroes

Easy

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

 

package leetcode.easy;

public class MoveZeroes {
	public void moveZeroes1(int[] nums) {
		int n = nums.length;

		// Count the zeroes
		int numZeroes = 0;
		for (int i = 0; i < n; i++) {
			if (nums[i] == 0) {
				numZeroes++;
			}
		}

		// Make all the non-zero elements retain their original order.
		java.util.ArrayList<Integer> ans = new java.util.ArrayList<Integer>();
		for (int i = 0; i < n; i++) {
			if (nums[i] != 0) {
				ans.add(nums[i]);
			}
		}

		// Move all zeroes to the end
		while (numZeroes > 0) {
			ans.add(0);
			numZeroes--;
		}

		// Combine the result
		for (int i = 0; i < n; i++) {
			nums[i] = ans.get(i);
		}
	}

	public void moveZeroes2(int[] nums) {
		int lastNonZeroFoundAt = 0;
		// If the current element is not 0, then we need to
		// append it just in front of last non 0 element we found.
		for (int i = 0; i < nums.length; i++) {
			if (nums[i] != 0) {
				nums[lastNonZeroFoundAt++] = nums[i];
			}
		}
		// After we have finished processing new elements,
		// all the non-zero elements are already at beginning of array.
		// We just need to fill remaining array with 0's.
		for (int i = lastNonZeroFoundAt; i < nums.length; i++) {
			nums[i] = 0;
		}
	}

	public void moveZeroes3(int[] nums) {
		for (int lastNonZeroFoundAt = 0, cur = 0; cur < nums.length; cur++) {
			if (nums[cur] != 0) {
				int temp = nums[lastNonZeroFoundAt];
				nums[lastNonZeroFoundAt] = nums[cur];
				nums[cur] = temp;
				lastNonZeroFoundAt++;
			}
		}
	}

	private void print_arr(int[] array) {
		for (int i = 0; i < array.length; i++) {
			System.out.print(array[i] + " ");
		}
		System.out.println();
	}

	@org.junit.Test
	public void test1() {
		int[] nums = { 0, 1, 0, 3, 12 };
		print_arr(nums);
		moveZeroes1(nums);
		print_arr(nums);
	}

	@org.junit.Test
	public void test2() {
		int[] nums = { 0, 1, 0, 3, 12 };
		print_arr(nums);
		moveZeroes2(nums);
		print_arr(nums);
	}

	@org.junit.Test
	public void test3() {
		int[] nums = { 0, 1, 0, 3, 12 };
		print_arr(nums);
		moveZeroes3(nums);
		print_arr(nums);
	}
}