LeetCode 219 Contains Duplicate II

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.

Summary:

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。

Solution:

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。

 class Solution {
 public:
     bool containsNearbyDuplicate(vector<int>& nums, int k) {
         int len = nums.size();
         unordered_map<int, int> m;

         for (int i = ; i < len; i++) {
             if (m.find(nums[i]) != m.end() && i - m[nums[i]] <= k) {
                 return true;
             }
             else {
                 m[nums[i]] = i;
             }
         }

         return false;
     }
 };