Solved Challenge

src/index.js

@@ -4,7 +4,32 @@
  * @returns {number[][]}
  */
 const findNodesWithZeroAndOneParents = (parentChildPairs) => {
+    const result = [[],[]];
+
+    const countOfParentsPerChild = parentChildPairs.reduce((dictionary, pair) => {
+        if (dictionary[pair[1]])
+            dictionary[pair[1]]++;
+        else
+            dictionary[pair[1]] = 1;
+        return dictionary;
+    }, {});
 
+
+    const oneParentChildren = Object.keys(countOfParentsPerChild)
+        .filter(child => countOfParentsPerChild[child] === 1)
+        .map(childKey => parseInt(childKey));
+
+    let zeroParentsChildren = Array.from(
+        new Set(
+            parentChildPairs.map(pair => pair[0])
+                .filter(child => !(child in countOfParentsPerChild))
+        )
+    );
+
+    result[0] = zeroParentsChildren;
+    result[1] = oneParentChildren;
+
+    return result;
 }
 
 module.exports = findNodesWithZeroAndOneParents;