哈希表

Problem:

219. 存在重复元素 II

思路

先开用的暴力，结果有个样例超时了，然后改用哈希表

Code

暴力枚举

class Solution {
    public boolean containsNearbyDuplicate(int[] nums, int k) {
        int n = nums.length;
        boolean res = false;
        for (int i = 0; i < n; i++) {
            for (int j = i + 1; j < n && j <= i + k; j++) {
                if (nums[i] == nums[j] && Math.abs(i - j) <= k) {
                    res = true;
                }
            }
        }
        return res;
    }
}

哈希表

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