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Contains Duplicate II

描述

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.

分析

维护一个 HashMap, key 为整数,value 为下标,将数组中的元素不断添加进这个 HashMap, 碰到重复时,计算二者的下标距离,如果距离小于或等于 k,则返回 true, 如果直到数组扫描完,距离都大于 k,则返回 false。

代码

// Contains Duplicate II
// Time Complexity: O(n), Space Complexity: O(n)
public class Solution {
public boolean containsNearbyDuplicate(int[] nums, int k) {
final Map<Integer, Integer> map = new HashMap<>();
int min = Integer.MAX_VALUE;

for(int i = 0; i < nums.length; i++){
if(map.containsKey(nums[i])){
final int preIndex = map.get(nums[i]);
final int gap = i - preIndex;
min = Math.min(min, gap);
}
map.put(nums[i], i);
}
return min <= k;
}
}