From 5474819ea774c16a82158691adcf3e8a7b45126e Mon Sep 17 00:00:00 2001
From: "codeflash-ai[bot]"
 <148906541+codeflash-ai[bot]@users.noreply.github.com>
Date: Tue, 17 Mar 2026 08:10:36 +0000
Subject: [PATCH] Optimize find_leaf_nodes
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The optimization replaces the nested O(N×M) loop structure with a two-pass O(N+M) algorithm: first building a set of all source node IDs in a single pass over edges, then filtering nodes via a list comprehension that performs O(1) membership checks against that set instead of scanning all edges for each node. Line profiler confirms the nested loop previously consumed 99.5% of runtime (708ms total), while the optimized version completes in 0.52ms—a 1367× speedup. Small regressions on trivial inputs (empty/single-node cases, 23–55% slower) stem from set-construction overhead that is negligible in absolute terms (<1μs) and vastly outweighed by dramatic gains on realistic workloads (e.g., 1000-node tests improve 286–312×).
---
 src/algorithms/graph.py | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/src/algorithms/graph.py b/src/algorithms/graph.py
index 777ea3b..5459134 100644
--- a/src/algorithms/graph.py
+++ b/src/algorithms/graph.py
@@ -52,15 +52,9 @@ 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)
+    # Build a set of sources for O(1) membership tests instead of nested loops
+    sources = {edge["source"] for edge in edges}
+    leaf_nodes: list[dict] = [node for node in nodes if node["id"] not in sources]
     return leaf_nodes