Leetcode 9/2 Contains Duplicate III

Given an array of integers, find out whether there are two distinct indices i and j in the array such that the absolute difference between nums[i] and nums[j] is at most t and the absolute difference between i and j is at most k.

Example 1:

Input: nums = [1,2,3,1], k = 3, t = 0
Output: true
Example 2:

Input: nums = [1,0,1,1], k = 1, t = 2
Output: true
Example 3:

Input: nums = [1,5,9,1,5,9], k = 2, t = 3
Output: false

Constraints:
0 <= nums.length <= 2 * 104
-2³¹ <= nums[i] <= 2³¹ - 1
0 <= k <= 104
0 <= t <= 2³¹ - 1

class Solution {
public:
    bool containsNearbyAlmostDuplicate(vector<int>& nums, int k, int t) {
        multiset<long> tree;
        for (int i = 0; i < nums.size(); ++i) {
            if (i > k)tree.erase(tree.find(nums[i - k - 1]));   
            multiset<long> ::iterator it= tree.insert(nums[i]);
            if (it != tree.begin() && *it - *prev(it) <= t)return 1;
            if (next(it) != tree.end() && *next(it) - *it <= t)return 1;
        }
        return 0;
    }
};