Given an array of integers and an integer k, find out whether there are two distinct indices i and j in the array such that numsi = numsj and the absolute difference between i and j is at most k.
217的升级版，https://cloud.tencent.com/developer/article/1019114
要求判断是否存在重复的数之间的下标距离不超过k。
出现过的数和之前的下标求绝对值，超过K则放弃前面的下标，记录新下标。
代码语言：javascript复制class Solution {
public:
bool containsNearbyDuplicate(vector<int>& nums, int k) {
unordered_map<int, int> mp;
for(int i = 0; i < nums.size(); i )
{
if(mp.find(nums[i]) == mp.end()) mp[nums[i]] = i;
else if(abs(mp[nums[i]]-i) <= k) return true;
else mp[nums[i]] = i;
}
return false;
}
};
