_0027_RemoveElement.java

package com.diguage.algorithm.leetcode;

import java.util.Arrays;

/**
 * = 27. Remove Element
 *
 * https://leetcode.com/problems/remove-element/description/[Remove Element - LeetCode]
 *
 * Given an array `nums` and a value `val`, remove all instances of that value
 * *https://en.wikipedia.org/wiki/In-place_algorithm[in-place]* and return the new length.
 *
 * Do not allocate extra space for another array, you must do this by *modifying
 * the input array* *https://en.wikipedia.org/wiki/In-place_algorithm[in-place]* with O(1) extra memory.
 *
 * The order of elements can be changed. It doesn't matter what you leave beyond the new length.
 *
 * .Example 1:
 * [source]
 * ----
 * Given nums = [3,2,2,3], val = 3,
 *
 * Your function should return length = 2, with the first two elements of nums being 2.
 *
 * It doesn't matter what you leave beyond the returned length.
 * ----
 *
 * .Example 1:
 * [source]
 * ----
 * Given nums = [0,1,2,2,3,0,4,2], val = 2,
 *
 * Your function should return length = 5, with the first five elements of nums containing 0, 1, 3, 0, and 4.
 *
 * Note that the order of those five elements can be arbitrary.
 *
 * It doesn't matter what values are set beyond the returned length.
 * ----
 *
 * == Clarification:
 *
 * Confused why the returned value is an integer but your answer is an array?
 *
 * Note that the input array is passed in by reference, which means modification to the input array will be known to the caller as well.
 *
 * Internally you can think of this:
 *
 * [source]
 * ----
 * // nums is passed in by reference. (i.e., without making a copy)
 * int len = removeElement(nums, val);
 *
 * // any modification to nums in your function would be known by the caller.
 * // using the length returned by your function, it prints the first len elements.
 * for (int i = 0; i < len; i++) {
 *     print(nums[i]);
 * }
 * ----
 *
 * @author D瓜哥, https://www.diguage.com/
 * @since 2018-07-19 18:55
 */
public class _0027_RemoveElement {
    public static int removeElement(int[] nums, int val) {
        if (nums == null || nums.length == 0) {
            return 0;
        }
        int result = nums.length;
        int minuendIndex = 0;
        for (int i = 0; i < nums.length; i++) {
            if (minuendIndex > 0) {
                nums[i - minuendIndex] = nums[i];
            }
            if (nums[i] == val) {
                result--;
                minuendIndex++;
            }
        }
        return result;
    }

    public static void main(String[] args) {
        int[] nums = new int[]{0, 1, 2, 2, 3, 0, 4, 2};
        int val = 2;
        System.out.println(removeElement(nums, val));
        System.out.println(Arrays.toString(nums));
    }
}