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// @Title: 省份数量 (Number of Provinces)
// @Author: 15816537946@163.com
// @Date: 2021-01-07 23:49:45
// @Runtime: 28 ms
// @Memory: 6.6 MB
func findCircleNum(isConnected [][]int) (ans int) {
	n := len(isConnected)
	parent := make([]int, n)
	for i := range parent {
		parent[i] = i
	}
	var find func(int) int
	find = func(x int) int {
		if parent[x] != x {
			parent[x] = find(parent[x])
		}
		return parent[x]
	}
	union := func(from, to int) {
		parent[find(from)] = find(to)
	}

	for i, row := range isConnected {
		for j := i + 1; j < n; j++ {
			if row[j] == 1 {
				union(i, j)
			}
		}
	}
	for i, p := range parent {
		if i == p {
			ans++
		}
	}
	return
}