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.
在数组中找两个相等的数，如果他们索引之差的绝对值 <= k 则返回true
C++(26ms):
1 class Solution { 2 public: 3 bool containsNearbyDuplicate(vector<int>& nums, int k) { 4 unordered_set<int> s ; 5 int len = nums.size() ; 6 for (int i = 0 ; i < len ; i++){ 7 if (i > k) 8 s.erase(nums[i-k-1]) ; 9 if (!s.insert(nums[i]).second) 10 return true ; 11 } 12 return false ; 13 } 14 };
C++（155ms）：
1 class Solution { 2 public: 3 bool containsNearbyDuplicate(vector<int>& nums, int k) { 4 unordered_map<int,int> Map ; 5 int len = nums.size() ; 6 bool flag = false ; 7 for (int i = 0; i < len;i++ ){ 8 if (Map[nums[i]]){ 9 int t = abs(i+1 - Map[nums[i]]) ; 10 Map[nums[i]] = i+1 ; 11 if (t <= k){ 12 flag = true ; 13 break ; 14 } 15 }else{ 16 Map[nums[i]] = i+1 ; 17 cout<<Map[nums[i]]<<endl ; 18 } 19 } 20 if (flag) 21 return true ; 22 else 23 return false ; 24 } 25 };