(leetcode)Contains Duplicate II

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 iand j is at most k.

 

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