Leetcode
2020.05.04 10:04
532. K-diff Pairs in an Array
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Given an array of integers and an integer k, you need to find the number of unique k-diff pairs in the array. Here a k-diff pair is defined as an integer pair (i, j), where i and j are both numbers in the array and their absolute difference is k.
Example 1:
Input: [3, 1, 4, 1, 5], k = 2 Output: 2 Explanation: There are two 2-diff pairs in the array, (1, 3) and (3, 5).
Although we have two 1s in the input, we should only return the number of unique pairs.
Example 2:
Input:[1, 2, 3, 4, 5], k = 1 Output: 4 Explanation: There are four 1-diff pairs in the array, (1, 2), (2, 3), (3, 4) and (4, 5).
Example 3:
Input: [1, 3, 1, 5, 4], k = 0 Output: 1 Explanation: There is one 0-diff pair in the array, (1, 1).
Note:
- The pairs (i, j) and (j, i) count as the same pair.
- The length of the array won't exceed 10,000.
- All the integers in the given input belong to the range: [-1e7, 1e7].
class Solution {
public int findPairs(int[] nums, int k) {
Map<String, Integer> hmap = new HashMap<>();
for(int i=0; i<nums.length-1; i++){
for(int j=i+1; j<nums.length; j++){
if(Math.abs(nums[i] - nums[j]) == k){
String key = Math.min(nums[i], nums[j]) + ":" + Math.max(nums[i], nums[j]);
hmap.put(key, hmap.getOrDefault(key,0)+1);
}
}
}
return hmap.size();
}
}class Solution {
public int findPairs(int[] nums, int k) {
Set<Integer> hset = new HashSet<>();
int count = 0;
Arrays.sort(nums);
for(int i=0; i<nums.length; i++){
if(hset.contains(nums[i])){
continue;
}
hset.add(nums[i]);
if(findDiff(nums, i+1, nums.length-1, nums[i]+k) == true){
count++;
}
}
return count;
}
//binary search
public boolean findDiff(int[] nums, int start, int end, int target){
if(start > end){
return false;
}
int mid = start + (end-start)/2;
if(nums[mid] == target){
return true;
}else if(nums[mid] < target){
return findDiff(nums, mid+1, end, target);
}else{
return findDiff(nums, start, mid-1, target);
}
}
}class Solution {
public int findPairs(int[] nums, int k) {
int count = 0;
long prev = Long.MAX_VALUE;
Arrays.sort(nums);
for(int i=0; i<nums.length; i++){
if(prev == nums[i]){
continue;
}
prev = nums[i];
if(findDiff(nums, i+1, nums.length-1, nums[i]+k) == true){
count++;
}
}
return count;
}
//binary search
public boolean findDiff(int[] nums, int start, int end, int target){
if(start > end){
return false;
}
int mid = start + (end-start)/2;
if(nums[mid] == target){
return true;
}else if(nums[mid] < target){
return findDiff(nums, mid+1, end, target);
}else{
return findDiff(nums, start, mid-1, target);
}
}
}[문제] https://leetcode.com/problems/k-diff-pairs-in-an-array/
