[Leetcode / hashtable] Duplicate element (sliding window + hash table)

Problem Description:

Given an integer array and an integer  K , if there are two different indexes in the array is determined  i  and  j , such that  the nums [i] = the nums [j] , and i and j  maximum absolute value of the difference K .

Example 1:

Input: the nums = [1,2,3,1], K  =. 3
 Output: to true

Example 2:

Input: the nums = [1,0,1,1], K  =  . 1
 Output: to true

Example 3:

Input: the nums = [1,2,3,1,2,3], K  =  2
 Output: to false

The basic idea:

Using the idea sliding window + hash set.

In the case of beginning the sliding window does not completely established, a special determination.

In the case of completion has been established, continue to delete and insert elements. To see if there are duplicate.

AC Code:

class Solution {
public:
    bool containsNearbyDuplicate(vector<int>& nums, int k) {
      int i = 0, j = 0;
      set<int> s;
      while (j != nums.size()) {
        if (s.size() != k + 1) {    // 处理刚开始的情况
          if (s.count(nums[j])) {   // 刚开始就有重复元素的情况
            return true;
          } else {
            s.insert(nums[j++]);
          }
        } else {    // 滑动窗口已经建立的情况下
          s.erase(nums[i++]);
          if (s.count(nums[j])) {
            return true;
          } else {
            s.insert(nums[j++]);
          }
        }
      }
      return false;
    }
};