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
     
      & nums, int k) { 4         unordered_set
      
        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
     
      & nums, int k) { 4         unordered_map
      
        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<
       
        <