0219. Contains Duplicate II
https://leetcode.com/problems/contains-duplicate-ii
Description
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
ac1: just hash map
class Solution {
public boolean containsNearbyDuplicate(int[] nums, int k) {
Map<Integer, Integer> hash = new HashMap<Integer, Integer>();
for (int i = 0; i < nums.length; i++) {
if (hash.containsKey(nums[i]) && i - hash.get(nums[i]) <= k) {
return true;
}
hash.put(nums[i], i);
}
return false;
}
}
ac2: sliding window
class Solution {
public boolean containsNearbyDuplicate(int[] nums, int k) {
int l = 0, r = 0;
HashSet<Integer> set = new HashSet<>();
while (r < nums.length) {
if (r - l > k) {
set.remove(nums[l++]);
}
if (set.contains(nums[r])) {
return true;
} else {
set.add(nums[r++]);
}
}
return false;
}
}
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