LeetCode219. Contains Duplicate II

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 absolute difference between i and j is at most k.

Example 1:

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Input: nums = [1,2,3,1], k = 3
Output: true

Example 2:

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Input: nums = [1,0,1,1], k = 1
Output: true

Example 3:

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Input: nums = [1,2,3,1,2,3], k = 2
Output: false

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Hash table

适用无序关联式容器,unordered_map<int,int>,key是数字,value是坐标的映射,如果哈希表中存在这个数字,并且当前数字的索引减去这个数字的索引小于等于k,就返回真,否则将这个数字的索引存入哈希表中。

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bool containsNearbyDuplicate(vector<int>& nums, int k) {
unordered_map<int,int> m;
for(int i=0;i<nums.size();i++)
{
if(m.find(nums[i])!=m.end() && i-m[nums[i]]<=k) return true;
m[nums[i]]=i;
}
return false;
}
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