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
Solutions
My solution
class Solution {
public:
bool containsNearbyDuplicate(vector<int>& nums, int k) {
unordered_map<int, int> hash; // hash[num]: frequency of num in the sliding window of length k
for(int i = 0; i < nums.size(); ++i){
if(++hash[nums[i]] > 1)
return true;
if(i >= k)
--hash[nums[i - k]];
}
return false;
}
};
Another solution
class Solution {
public:
bool containsNearbyDuplicate(vector<int>& nums, int k) {
unordered_map<int, int> hash; // hash[num]: the index of the last occurrence of num
for(int i = 0; i < nums.size(); ++i){
auto it = hash.find(nums[i]);
if(it != hash.end() && i - it->second <= k)
return true;
hash[nums[i]] = i;
}
return false;
}
};
