leetcode---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 j is at most k.

class Solution { public: bool containsNearbyDuplicate(vector<int>& nums, int k) { int n = nums.size(); map<int, int> m; for(int i=0; i<n; i++) { if(m.find(nums[i]) != m.end() && i - m[nums[i]] <= k) return true; m[nums[i]] = i; } return false; } };