Added solution to find longest unique nodes path

YogenRaii · YogenRaii · commit 4136811dcd2d · 2019-06-30T09:33:45.000-05:00
diff --git a/src/main/java/com/eprogrammerz/examples/algorithm/trees/LongestUniquePath.java b/src/main/java/com/eprogrammerz/examples/algorithm/trees/LongestUniquePath.java
@@ -0,0 +1,73 @@
+package com.eprogrammerz.examples.algorithm.trees;
+
+import org.junit.Test;
+
+import java.util.*;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * Find longest path with unique node ids in given tree
+ */
+public class LongestUniquePath {
+    /**
+     *         6
+     *       /   \
+     *      3     7
+     *     / \     \
+     *    2   5     6
+     *         \     \
+     *          1     10
+     *                 \
+     *                  7
+     *   Unique path: [6,3,5,1]
+     */
+
+    public int longestUniquePath(TreeNode root) {
+        Set<Integer> path = new HashSet<>();
+        traversal(root, path, new ArrayList<>());
+        return path.size();
+    }
+
+    private void traversal(TreeNode node, Set<Integer> path, ArrayList<Integer> temp) {
+        if (node == null) return;
+        // visit
+        temp.add(node.val);
+
+        if (node.left == null && node.right == null) {
+            Set<Integer> result = new HashSet<>(temp);
+            if (result.size() > path.size()) {
+                path.clear();
+                path.addAll(result);
+                temp.remove(temp.size() - 1);
+            }
+            return;
+        }
+
+        traversal(node.left, path, temp);
+        traversal(node.right, path, temp);
+        temp.remove(temp.size() - 1);
+    }
+
+    @Test
+    public void testPathSum() {
+        TreeNode root = new TreeNode(6);
+        root.left = new TreeNode(3);
+        root.right = new TreeNode(7);
+
+        root.right.right = new TreeNode(6);
+
+        root.left.left = new TreeNode(2);
+        root.left.right = new TreeNode(5);
+        root.left.right.right = new TreeNode(1);
+
+        assertEquals(4, longestUniquePath(root));
+
+        // add right node to rightest node on last level
+        root.right.right.right = new TreeNode(10);
+        root.right.right.right.right = new TreeNode(7);
+
+        assertEquals(4, longestUniquePath(root));
+
+    }
+}
