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 absolute difference between i and j is at most k.
Example 1:
Input: nums = [1,2,3,1], k = 3
Output: true
Example 2:
Input: nums = [1,0,1,1], k = 1
Output: true
Example 3:
Input: nums = [1,2,3,1,2,3], k = 2
Output: false
// Hash map
bool containsNearbyDuplicate(vector<int>& nums, int k) { // time: O(n); space: O(n)
unordered_map<int, int> mp;
for (int i = 0; i < nums.size(); ++i) {
if (mp.count(nums[i]) && i - mp[nums[i]] <= k) {
return true;
}
mp[nums[i]] = i;
}
return false;
}
// Hash set
bool containsNearbyDuplicate(vector<int>& nums, int k) { // time: O(n); space: O(n)
unordered_set<int> st;
for (int i = 0; i < nums.size(); ++i) {
if (i > k) {
st.erase(nums[i - k - 1]);
}
if (st.count(nums[i])) return true;
st.insert(nums[i]);
}
return false;
}