- Difficulty: Hard
- Tags: LeetCode, Hard, Union Find, Graph, Minimum Spanning Tree, Heap (Priority Queue), leetcode-1168, O(nlogn), O(n), 🔒
Problem
There are n
houses in a village. We want to supply water for all the houses by building wells and laying pipes.
For each house i
, we can either build a well inside it directly with cost wells[i - 1]
(note the -1
due to 0-indexing), or pipe in water from another well to it. The costs to lay pipes between houses are given by the array pipes
where each pipes[j] = [house1j, house2j, costj]
represents the cost to connect house1j
and house2j
together using a pipe. Connections are bidirectional, and there could be multiple valid connections between the same two houses with different costs.
Return the minimum total cost to supply water to all houses.
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Example 1:
Input: n = 3, wells = [1,2,2], pipes = [[1,2,1],[2,3,1]] Output: 3 Explanation: The image shows the costs of connecting houses using pipes. The best strategy is to build a well in the first house with cost 1 and connect the other houses to it with cost 2 so the total cost is 3.
Example 2:
Input: n = 2, wells = [1,1], pipes = [[1,2,1],[1,2,2]] Output: 2 Explanation: We can supply water with cost two using one of the three options: Option 1: - Build a well inside house 1 with cost 1. - Build a well inside house 2 with cost 1. The total cost will be 2. Option 2: - Build a well inside house 1 with cost 1. - Connect house 2 with house 1 with cost 1. The total cost will be 2. Option 3: - Build a well inside house 2 with cost 1. - Connect house 1 with house 2 with cost 1. The total cost will be 2. Note that we can connect houses 1 and 2 with cost 1 or with cost 2 but we will always choose the cheapest option.
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Constraints:
2 <= n <= 104
wells.length == n
0 <= wells[i] <= 105
1 <= pipes.length <= 104
pipes[j].length == 3
1 <= house1j, house2j <= n
0 <= costj <= 105
house1j != house2j