Leetcode219/220 存在重复元素2/3 hashmap优化以及treemap优化

hashmap/hashset优化到O(n), 带一点滑动窗口思想。

class Solution {
public:
    bool containsNearbyDuplicate(vector<int>& nums, int k) {
        unordered_set<int> hashset;
        int n = nums.size();
        for(int i=0;i<n;i++){
            if(hashset.count(nums[i])) return true;
            else hashset.insert(nums[i]);
            if(i>=k) hashset.erase(nums[i-k]);
        }
        return false;
    }
};

用红黑树加lower_bound优化到O(nlogk） 

class Solution {
public:
    bool containsNearbyAlmostDuplicate(vector<int>& nums, int k, int t) {
        set<long long> treeSet;
        for(int i=0;i<nums.size();i++){
            auto it = treeSet.lower_bound((long long)nums[i]-t);
            if(it!=treeSet.end()&&*it<=(long long)nums[i]+t) return true;
            treeSet.insert(nums[i]);
            if(treeSet.size()==k+1) treeSet.erase(nums[i-k]);
        }
        return false;
    }
};

 

 

 

来源：oschina

链接：https://my.oschina.net/u/4278651/blog/4483509