leetcode219v2.cpp

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