Contains Duplicate II

问题：

Given an array of integers and an integer k, find out whether there there are two distinct indices i and j in the array such that nums[i] = nums[j] and the difference between iand j is at most k.

思路：

　hash表

我的代码：

public class Solution {
    public boolean containsNearbyDuplicate(int[] nums, int k) {
        if(nums==null || nums.length==0 || k<0 ) return false;
        HashMap<Integer,Integer> hash = new HashMap<Integer,Integer>();
        for(int i=0; i<nums.length; i++)
        {
            if(hash.containsKey(nums[i]))
            {
                if(i-hash.get(nums[i]) <= k) return true;
                hash.put(nums[i], i);
            }
            else 
                hash.put(nums[i], i);
        }
        return false;
    }
}

View Code

学习之处：

在数组里面的坐标问题可以考虑用hashtable进行存储，用空间换时间是一个常用的策略。