_1361.java

packagecom.fishercoder.solutions.secondthousand;

importjava.util.ArrayList;
importjava.util.HashMap;
importjava.util.List;
importjava.util.Map;

publicclass_1361 {
publicstaticclassSolution1 {
publicbooleanvalidateBinaryTreeNodes(intn, int[] leftChild, int[] rightChild) {
int[] indegree = newint[n];
for (inti = 0; i < n; i++) {
if (leftChild[i] >= 0) {
indegree[leftChild[i]]++;
 }
if (rightChild[i] >= 0) {
indegree[rightChild[i]]++;
 }
 }
// only one node has in-degree = 0
intindegreeZero = 0;
for (intnum : indegree) {
if (num == 0) {
indegreeZero++;
if (indegreeZero > 1) {
returnfalse;
 }
 }
// every other node's in-degree must be exactly equal to 1
if (num > 1) {
returnfalse;
 }
 }
// no bi-directional pointing
Map<Integer, List<Integer>> map = newHashMap<>();
for (inti = 0; i < n; i++) {
map.put(i, newArrayList<>());
map.get(i).add(leftChild[i]);
map.get(i).add(rightChild[i]);
 }
for (intnode : map.keySet()) {
List<Integer> children = map.get(node);
for (intchild : children) {
if (map.containsKey(child) && map.get(child).contains(node)) {
returnfalse;
 }
 }
 }
returntrue;
 }
 }
}