LeetCode 219:Contains Duplicate II

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 nums[i] = nums[j] and
the difference between i and jis
at most k.

//给出一个整数数组，判断该数组内是否有两个元素值是相同的，且他们的索引值相差不大于k，是则返回true，否则返回false
 class Solution {
 public:
	 bool containsNearbyDuplicate(vector<int>& nums, int k) {
		 map<int, int> buf;
		 int n = nums.size();
		 for (int i = 0; i < n; i++)
		 {
			 if (buf.find(nums[i]) != buf.end() && i - buf[nums[i]] <= k)
			 {
				 return true;
			 }
			 else
			 {
				 buf[nums[i]] = i;
			 }
		 }

		 return false;
	 }
 };