LeetCode 219 Contains Duplicate II

Posted 2020-08-25 SillyVicky

Problem:

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 difference between i and j is at most k.

Analysis:

给出数组nums，整型数k，找到数组中是否存在nums[i]和nums[j]相等且i - j小于k的情况。

Summary:

开始用最简单写法，两重for循环逐一查找，出现TLE。

后用HashMap改进，key为数组中出现的数字，value为最近出现位置的下标。

 1 class Solution {
 2 public:
 3     bool containsNearbyDuplicate(vector<int>& nums, int k) {
 4         int len = nums.size();
 5         unordered_map<int, int> m;
 6         
 7         for (int i = 0; i < len; i++) {
 8             if (m.find(nums[i]) != m.end() && i - m[nums[i]] <= k) {
 9                 return true;
10             }
11             else {
12                 m[nums[i]] = i;
13             }
14         }
15         
16         return false;
17     }
18 };