Contains Duplicate II

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;
}
}

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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。