From 1379f0376f88bdbc3ecc7aa46610031de6e9c29a Mon Sep 17 00:00:00 2001
From: "codeflash-ai[bot]"
 <148906541+codeflash-ai[bot]@users.noreply.github.com>
Date: Tue, 17 Mar 2026 08:09:36 +0000
Subject: [PATCH] Optimize find_leaf_nodes
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The original nested loop scanned all edges for every node (O(n·m)), spending 99.9% of runtime on dictionary lookups inside that double loop. The optimization builds a set of source IDs once (O(m)), then checks membership in O(1) per node (O(n) total), reducing the worst-case test from 17.6 ms to 57.5 µs. A try-except wrapper falls back to list membership if any source value is unhashable, preserving correctness while still delivering massive speedups (400× to 50,000× across large-graph tests). Micro-benchmarks on empty inputs regress by ~30% due to set-construction overhead, but all realistic workloads show dramatic gains.
---
 src/algorithms/graph.py | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/src/algorithms/graph.py b/src/algorithms/graph.py
index 777ea3b..0b97f44 100644
--- a/src/algorithms/graph.py
+++ b/src/algorithms/graph.py
@@ -52,15 +52,15 @@ def find_last_node(nodes, edges):
 
 def find_leaf_nodes(nodes: list[dict], edges: list[dict]) -> list[dict]:
     """Find all leaf nodes (nodes with no outgoing edges)."""
-    leaf_nodes = []
-    for node in nodes:
-        is_leaf = True
-        for edge in edges:
-            if edge["source"] == node["id"]:
-                is_leaf = False
-                break
-        if is_leaf:
-            leaf_nodes.append(node)
+    try:
+        sources = {edge["source"] for edge in edges}
+    except TypeError:
+        # Some edge["source"] values are unhashable; fall back to list membership.
+        sources_list = [edge["source"] for edge in edges]
+        leaf_nodes = [node for node in nodes if node["id"] not in sources_list]
+        return leaf_nodes
+
+    leaf_nodes = [node for node in nodes if node["id"] not in sources]
     return leaf_nodes