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Java-based LeetCode algorithm problem solutions, regularly updated
1627\. Graph Connectivity With Threshold
Hard
We have `n` cities labeled from `1` to `n`. Two different cities with labels `x` and `y` are directly connected by a bidirectional road if and only if `x` and `y` share a common divisor **strictly greater** than some `threshold`. More formally, cities with labels `x` and `y` have a road between them if there exists an integer `z` such that all of the following are true:
* `x % z == 0`,
* `y % z == 0`, and
* `z > threshold`.
Given the two integers, `n` and `threshold`, and an array of `queries`, you must determine for each queries[i] = [ai, bi]
if cities ai
and bi
are connected directly or indirectly. (i.e. there is some path between them).
Return _an array_ `answer`_, where_ `answer.length == queries.length` _and_ `answer[i]` _is_ `true` _if for the_ ith
_query, there is a path between_ ai
_and_ bi
_, or_ `answer[i]` _is_ `false` _if there is no path._
**Example 1:**
![](https://assets.leetcode.com/uploads/2020/10/09/ex1.jpg)
**Input:** n = 6, threshold = 2, queries = [[1,4],[2,5],[3,6]]
**Output:** [false,false,true]
**Explanation:** The divisors for each number:
1: 1
2: 1, 2
3: 1, 3
4: 1, 2, 4
5: 1, 5
6: 1, 2, 3, 6
Using the underlined divisors above the threshold, only cities 3 and 6 share a common divisor, so they are the only ones directly connected. The result of each query:
[1,4] 1 is not connected to 4
[2,5] 2 is not connected to 5
[3,6] 3 is connected to 6 through path 3--6
**Example 2:**
![](https://assets.leetcode.com/uploads/2020/10/10/tmp.jpg)
**Input:** n = 6, threshold = 0, queries = [[4,5],[3,4],[3,2],[2,6],[1,3]]
**Output:** [true,true,true,true,true]
**Explanation:** The divisors for each number are the same as the previous example. However, since the threshold is 0, all divisors can be used. Since all numbers share 1 as a divisor, all cities are connected.
**Example 3:**
![](https://assets.leetcode.com/uploads/2020/10/17/ex3.jpg)
**Input:** n = 5, threshold = 1, queries = [[4,5],[4,5],[3,2],[2,3],[3,4]]
**Output:** [false,false,false,false,false]
**Explanation:** Only cities 2 and 4 share a common divisor 2 which is strictly greater than the threshold 1, so they are the only ones directly connected. Please notice that there can be multiple queries for the same pair of nodes [x, y], and that the query [x, y] is equivalent to the query [y, x].
**Constraints:**
* 2 <= n <= 104
* `0 <= threshold <= n`
* 1 <= queries.length <= 105
* `queries[i].length == 2`
* 1 <= ai, bi <= cities
* ai != bi