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685.java
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685.java
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__________________________________________________________________________________________________
sample 0 ms submission
class Solution {
public int[] findRedundantDirectedConnection(int[][] edges) {
int n = edges.length;
int[] parent = new int[n+1], ds = new int[n+1];
Arrays.fill(parent, -1);
int first = -1, second = -1, last = -1;
for(int i = 0; i < n; i++) {
int p = edges[i][0], c = edges[i][1];
if (parent[c] != -1) {
first = parent[c];
second = i;
continue;
}
parent[c] = i;
int p1 = find(ds, p);
if (p1 == c) last = i;
else ds[c] = p1;
}
if (last == -1) return edges[second]; // no cycle found by removing second
if (second == -1) return edges[last]; // no edge removed
return edges[first];
}
private int find(int[] ds, int i) {
return ds[i] == 0 ? i : (ds[i] = find(ds, ds[i]));
}
}
__________________________________________________________________________________________________
sample 37380 kb submission
class Solution {
public int[] findRedundantDirectedConnection(int[][] edges) {
if (edges == null || edges.length == 0 || edges[0] == null || edges[0].length == 0)
return null;
Set<Integer> points = new HashSet<>();
Map<Integer, Integer> parent = new HashMap<>();
List<int[]> candidates = new ArrayList<>();
for (int[] edge : edges) {
int src = edge[0];
int dst = edge[1];
points.add(src);
points.add(dst);
if (!parent.containsKey(dst)) {
parent.put(dst, src);
continue;
}
candidates.add(new int[]{src, dst});
candidates.add(new int[]{parent.get(dst), dst});
edge[1] = 0;
}
UnionFind uf = new UnionFind(points.size());
for (int[] edge : edges) {
if (edge[1] == 0)
continue;
int src = edge[0] - 1;
int dst = edge[1] - 1;
if (uf.isUnion(src, dst)) {
if (candidates.size() == 0)
return edge;
return candidates.get(1);
}
uf.union(src, dst);
}
return candidates.get(0);
}
class UnionFind{
private int[] uf;
UnionFind(int n) {
uf = new int[n];
for (int i = 0; i < n; i++) {
uf[i] = i;
}
}
private int getRoot(int i) {
while (i != uf[i]) {
i = uf[i];
}
return i;
}
public void union(int i, int j) {
int rooti = getRoot(i);
int rootj = getRoot(j);
uf[rooti] = rootj;
}
public boolean isUnion(int i, int j) {
return getRoot(i) == getRoot(j);
}
}
}
__________________________________________________________________________________________________