- Contains Duplicate II
Easy
Given an integer array nums and an integer k, return true if there are two distinct indices i and j in the array such that nums[i] == nums[j] and abs(i - j) <= 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
Constraints:
1 <= nums.length <= 105
-109 <= nums[i] <= 109
0 <= k <= 105
Solution 1: Just use simple unordered_map
class Solution {
public:
bool containsNearbyDuplicate(vector<int>& nums, int k) {
int n = nums.size();
unordered_map<int, int> s; //<num, index>
for (int i = 0; i < n; i++) {
if (s.find(nums[i]) != s.end() && (i - s[nums[i]] <= k)) {
return true;
}
s[nums[i]] = i;
}
return false;
}
};
Solution 2: sliding window
class Solution {
public:
bool containsNearbyDuplicate(vector<int>& nums, int k) {
int n = nums.size();
int left = 0, right = 0;
unordered_set<int> s;
while (right < n) {
s.insert(nums[right]);
right++;
while (right - left > k) {
s.erase(nums[left]);
left++;
}
if (right < n && s.find(nums[right]) != s.end()) return true;
}
return false;
}
};