[Swift]LeetCode323. 无向图中的连通区域的个数 $ Number of Connected Components in an Undirected Graph

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Given n nodes labeled from 0 to n - 1 and a list of undirected edges (each edge is a pair of nodes), write a function to find the number of connected components in an undirected graph.

Example 1:

     0          3

     |          |

     1 --- 2    4

Given n = 5 and edges = [[0, 1], [1, 2], [3, 4]], return 2.

Example 2:

     0           4

     |           |

     1 --- 2 --- 3

Given n = 5 and edges = [[0, 1], [1, 2], [2, 3], [3, 4]], return 1.

 Note:

You can assume that no duplicate edges will appear in edges. Since all edges are undirected, [0, 1] is the same as [1, 0] and thus will not appear together in edges.

---

给定n个标记为0到n-1的节点和无向边列表（每个边都是一对节点），编写一个函数来查找无向图中连接的组件的数量。

例1：

     0          3

     |          |

     1 --- 2    4

假设n=5，edges = [[0, 1], [1, 2], [3, 4]]，返回2。

例2：

     0           4

     |           |

     1 --- 2 --- 3

如果n=5，edges = [[0, 1], [1, 2], [2, 3], [3, 4]],返回1。

注：

可以假定边中不会出现重复的边。因为所有边都是无向的，[0，1]与[1，0]相同，因此不会出现在边中。

---

Solution:

class Solution {
    func countComponents(_ n:Int,_ edges:inout [[Int]]) -> Int {
        var res:Int = n
        var root:[Int] = [Int](repeating:0,count:n)
        for i in 0..<n
        {
            root[i] = i
        }
        for a in edges
        {
            var x:Int = find(&root, a[0])
            var y:Int = find(&root, a[1])
            if x != y
            {
                res -= 1
                root[y] = x
            }
        }
        return res
    }
    
    func find(_ root:inout [Int],_ i:Int) -> Int
    {
        var i = i
        while(root[i] != i)
        {
            i = root[i]
        }
        return i
    }
}

点击：Playground测试

let n1:Int = 5
var edge1:[[Int]] = [[0, 1], [1, 2], [3, 4]]
print(Solution().countComponents(n1,&edge1))
//Print 2
let n2:Int = 5
var edge2:[[Int]] = [[0, 1], [1, 2], [2, 3], [3, 4]]
print(Solution().countComponents(n2,&edge2))
//Print 1