219_Contains_Duplicate_II.cpp

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

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

    return false;
    }
};