题解 | #数组中重复的数字#

import java.util.*;


public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param numbers int整型一维数组 
     * @return int整型
     */
    public int duplicate (int[] numbers) {
        int[] tag = new int[10001];
        for (int i = 0; i < 10001; i++) {
            tag[i] = 0;
        }

        for (int j = 0; j < numbers.length; j++) {
            if (numbers[j] >= 0 && numbers[j] <= 10000 && tag[numbers[j]] == 0) {
                tag[numbers[j]]++;
            }
            else if (numbers[j] >= 0 && numbers[j] <= 10000)
                return numbers[j];
            else
                return -1;
        }
        return -1;
    }
}