[LeetCode 解题报告]219. 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 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

相等的两个数 |i-j| <= k 

class Solution {
public:
    bool containsNearbyDuplicate(vector<int>& nums, int k) {
        unordered_map<int, int> m;
        for (int i = 0; i < nums.size(); i ++) {
            if (m.find(nums[i]) != m.end() && i - m[nums[i]] <= k)
                return true;
            else
                m[nums[i]] = i;
        }
        return false;
    }
};