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| class Solution {
List<int[]>[] g;
public int minReorder(int n, int[][] connections) {
g = new List[n];
Arrays.setAll(g, k -> new ArrayList<>());
for (int[] c : connections) {
int a = c[0], b = c[1];
g[a].add(new int[]{b, 1});
g[b].add(new int[]{a, 0});
}
return dfs(0, -1);
}
private int dfs(int x, int pa) {
int ans = 0;
for (int[] e : g[x]) {
int y = e[0], c = e[1];
if (y != pa) {
ans += c + dfs(y, x);
}
}
return ans;
}
}
|
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