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 difference between i and j is at most k.
判断重复元素系列的第二题，这次不仅要找到是否存在重复元素，而且要求两元素下标之差不大于k，这个题用hash_table就比较合适了，见代码:
class Solution {
public:
bool containsNearbyDuplicate(vector<int>& nums, int k) {
unordered_map<int,int> hash_table;
int i=0;
for(i=0;i<nums.size();i++){
if(hash_table.find(nums[i])!=hash_table.end()&&i-hash_table[nums[i]]<=k)
return true;
hash_table[nums[i]]=i;
}
return false;
}
};
- [ TODO Contains Duplicate III]