LeetCode Array Easy 219. Contains Duplicate II

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Description

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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.

Example 1:

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

Example 2:

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

Example 3:

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

问题描述：给定一个数组和一个整数k 判断是否存在两个重复元素i,j 使i和j的差的绝对值不大于k 如果存在 返回true 否则返回false

思路，这里使用字典Dictionary保存元素和元素的索引。如果能找到元素，则计算当前元素和上一个元素的索引的差是否不大于k

public bool ContainsNearbyDuplicate(int[] nums, int k) {
        Dictionary<int,int> dic = new Dictionary<int,int>();
        for(int i = 0; i < nums.Length; i++){
            if(dic.ContainsKey(nums[i])){
                if(i - dic[nums[i]]<=k)
                    return true;
            }
             dic[nums[i]] = i;
        }
        return false;
    }