zoukankan      html  css  js  c++  java
  • LeetCode 532. K-diff Pairs in an Array

    原题链接在这里:https://leetcode.com/problems/k-diff-pairs-in-an-array/

    题目:

    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:

    1. The pairs (i, j) and (j, i) count as the same pair.
    2. The length of the array won't exceed 10,000.
    3. All the integers in the given input belong to the range: [-1e7, 1e7].

    题解:

    HashMap<Integer, Integer> hm 计数 num与出现次数.

    再iterate一遍hm, 看是否key+k也在hm中.

    Note: corner case 例如 k<0.

    Time Complexity: O(n), n = nums.length. Space: O(n).

    AC Java:

     1 public class Solution {
     2     public int findPairs(int[] nums, int k) {
     3         if(nums == null || nums.length == 0 || k < 0){
     4             return 0;
     5         }
     6         
     7         int res = 0;
     8         HashMap<Integer, Integer> hm = new HashMap<Integer, Integer>();
     9         for(int num : nums){
    10             hm.put(num, hm.getOrDefault(num, 0)+1);
    11         }
    12         
    13         for(Map.Entry<Integer, Integer> entry : hm.entrySet()){
    14             if(k == 0){
    15                 if(entry.getValue() > 1){
    16                     res++;
    17                 }
    18             }else{
    19                 if(hm.containsKey(entry.getKey()+k)){
    20                     res++;
    21                 }
    22             }
    23         }
    24         return res;
    25     }
    26 }

    类似Two Sum

  • 相关阅读:
    QT中文报错问题
    自动获取UILabel高度
    vi编辑器的使用
    命令例子
    WPF中textBlock 变色功能
    php 删除目录及子文件
    jquery autocomplete插件
    js日历选择控件
    centeros bash: ifconfig: command not found
    php 文件日志类
  • 原文地址:https://www.cnblogs.com/Dylan-Java-NYC/p/6680791.html
Copyright © 2011-2022 走看看