原题链接: https://oj.leetcode.com/problems/remove-element/

public int removeElement(int[] A, int elem) {
    if (A == null || A.length == 0) return 0;

    int length = A.length;
    int index = 0;

    for (int i = 0; i < length; i++) {
        if (A[i] == elem) {
            A[index] = A[length - 1];
            i--;
            length--;
        } else {
            index++;
        }
    }

    return index;
}