leetcode——219—— Contains Duplicate II

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

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

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