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35 lines
1.0 KiB
Markdown
35 lines
1.0 KiB
Markdown
# [219. Contains Duplicate II](https://leetcode.com/problems/contains-duplicate-ii/)
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## 题目
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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.
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Example 1:
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```c
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Input: nums = [1,2,3,1], k = 3
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Output: true
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```
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Example 2:
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```c
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Input: nums = [1,0,1,1], k = 1
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Output: true
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```
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Example 3:
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```c
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Input: nums = [1,2,3,1,2,3], k = 2
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Output: false
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```
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## 题目大意
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这是一道简单题，如果数组里面有重复数字，并且重复数字的下标差值小于等于 K 就输出 true，如果没有重复数字或者下标差值超过了 K ，则输出 flase。
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## 解题思路
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这道题可以维护一个只有 K 个元素的 map，每次只需要判断这个 map 里面是否存在这个元素即可。如果存在就代表重复数字的下标差值在 K 以内。map 的长度如果超过了 K 以后就删除掉 i-k 的那个元素，这样一直维护 map 里面只有 K 个元素。
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