Solution3.java

package com.usher.algorithm.offer;

import java.util.HashMap;
import java.util.Map;

/**
 * @Author: Usher
 * @Description:
 */
public class Solution3 {
    // Parameters:
    //    numbers:     an array of integers
    //    length:      the length of array numbers
    //    duplication: (Output) the duplicated number in the array number,length of duplication array is 1,so using duplication[0] = ? in implementation;
    //                  Here duplication like pointor in C/C++, duplication[0] equal *duplication in C/C++
    //    这里要特别注意~返回任意重复的一个，赋值duplication[0]
    // Return value:       true if the input is valid, and there are some duplications in the array number
    //                     otherwise false
    public boolean duplicate(int numbers[],int length,int [] duplication) {

        if (numbers == null){
            duplication[0] = -1;
            return false;
        }

        Map<Integer,Integer> map = new HashMap<>();

        for (int v : numbers){

            if (map.containsKey(v)){
                duplication[0] = v;
                return true;
            }
            else
                map.put(v,1);
        }
        return false;
    }
}