Suppose we have some input data describing a graph of relationships between parents and children over multiple generations. The data is formatted as a list of (parent, child) pairs, where each individual is assigned a unique positive integer identifier.
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For example, in this diagram, 3 is a child of 1 and 2, and 5 is a child of 4:
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1 2 4 15
\ / / | \ /
3 5 8 9
\ / \ \
6 7 11
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<p>
Sample input/output (pseudodata):
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parentChildPairs = [
(1, 3), (2, 3), (3, 6), (5, 6), (15, 9),
(5, 7), (4, 5), (4, 8), (4, 9), (9, 11)
]
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<p>
Write a function that takes this data as input and returns two collections: one containing all individuals with zero known parents, and one containing all individuals with exactly one known parent.
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<p>
Output may be in any order:
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findNodesWithZeroAndOneParents(parentChildPairs) => [
[1, 2, 4, 15], // Individuals with zero parents
[5, 7, 8, 11] // Individuals with exactly one parent
]
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n: number of pairs in the input
public static void main(String[] argv) {
int[][] parentChildPairs = new int[][]{
{1, 3},
{2, 3},
{3, 6},
{5, 6},
{15, 9},
{5, 7},
{4, 5},
{4, 8},
{4, 9},
{9, 11}};
findNodesWithZeroAndOneParents(parentChildPairs);
}
public static void findNodesWithZeroAndOneParents(int[][] parentChildPairs) {
Map<Integer, List<Integer>> childAncestor = new HashMap<>();
for (int[] parentChildPair : parentChildPairs) {
int parent = parentChildPair[0];
int child = parentChildPair[1];
if (!childAncestor.containsKey(child)) {
childAncestor.put(child, new ArrayList<>());
}
List<Integer> parentValue = childAncestor.get(child);
parentValue.add(parent);
childAncestor.put(child, parentValue);
}
System.out.println(childAncestor.toString());
dfs(childAncestor);
}
private static void dfs(Map<Integer, List<Integer>> childAncestor) {
Set<Integer> childerOneParent = new HashSet<>();
Set<Integer> parentWithOutParent = new HashSet<>();
for (Map.Entry<Integer, List<Integer>> parent : childAncestor.entrySet()) {
if (parent.getValue().size() == 1) {
childerOneParent.add(parent.getKey());
}
List<Integer> part = parent.getValue();
for (Integer p : part) {
if (!childAncestor.containsKey(p)) {
parentWithOutParent.add(p);
}
}
}
System.out.println(childerOneParent.toString() + " / " + parentWithOutParent.toString());
}
}
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