220. Contains Duplicate III

# Medium

Key idea: use map to store a sliding window with size of k. map.lower_bound()

很难理解这个函数的作用以及本题的解题思路，思路见链接：https://www.cnblogs.com/grandyang/p/4545261.html

C++

class Solution {
public:
    bool containsNearbyAlmostDuplicate(vector<int>& nums, int k, int t) {
        map<long long, int> m;
        int base = 0;
        for(int i = 0; i < nums.size(); i ++) {
            if(i - base > k) m.erase(nums[base++]);
            auto a = m.lower_bound((long long)nums[i]-t);
            if(a != m.end() && abs(a->first - nums[i]) <= t) 
                return true;
            m[nums[i]] = i;
        }
        return false;
    }
};