Leetcode 题目解析之 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 numsi = numsj and the difference between i and j is at most k.

建立一个map，key是出现过的元素，value是该元素的下标。若相同元素距离大于k，则更新下标。

    public boolean containsNearbyDuplicate(int[] nums, int k) {
        Map<Integer, Integer> map = new HashMap<Integer, Integer>();
        for (int i = 0; i < nums.length; i++) {
            if (map.containsKey(nums[i])) {
                if (i - map.get(nums[i]) <= k) {
                    return true;
                }
            }
            map.put(nums[i], i);
        }
        return false;
    }