219 Contains Duplicate II

链接：https://leetcode.com/problems/contains-duplicate-ii/
问题描述：
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 i and j is at most k.

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给出数组和k，如果找到nums[i] = nums[j] 而且i和j的差小于等于k，那么返回true，否则返回false；

class Solution {
public:
     bool containsNearbyDuplicate(vector<int>& nums, int k) {
        map<int,int> hm;

        for(int i=0;i<nums.size();i++)
        {
            if(hm.find(nums[i])!=hm.end()&&i-hm[nums[i]]<=k)
                return true;
            hm[nums[i]]=i;
        }
        return false;
    }
};