从java中的数组中删除特定索引 [英] Remove specific index from array in java

问题描述

我可以通过提及索引值从数组中删除特定元素吗?例如，我可以通过给 index 值 1 来删除字符 d 吗?

Can I remove a specific element from array by mentioning index value? For example can I remove the character d by giving index value 1?

char[] words = { 'c', 'd', 'f', 'h', 'j' };

推荐答案

如果您需要从数组中删除一个或多个元素而不将其转换为 List 或创建额外的数组，您可以在O(n) 不依赖于要移除的项目数.

If you need to remove one or multiple elements from array without converting it to List nor creating additional array, you may do it in O(n) not dependent on count of items to remove.

这里，a 是初始数组，int... r 是要删除的元素的不同有序索引(位置):

Here, a is initial array, int... r are distinct ordered indices (positions) of elements to remove:

public int removeItems(Object[] a, int... r) {
    int shift = 0;                             
    for (int i = 0; i < a.length; i++) {       
        if (shift < r.length && i == r[shift])  // i-th item needs to be removed
            shift++;                            // increment `shift`
        else 
            a[i - shift] = a[i];                // move i-th item `shift` positions left
    }
    for (int i = a.length - shift; i < a.length; i++)
        a[i] = null;                            // replace remaining items by nulls

    return a.length - shift;                    // return new "length"
}  

小测试:

Character[] words = {'c','d','f','h','j'};
removeItems(words, 1);
System.out.println(Arrays.asList(words));       // [c, f, h, j, null]

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