diff --git a/notes/pics/reverse-k-group.png b/notes/pics/reverse-k-group.png
index 61aabccb..42eef477 100644
Binary files a/notes/pics/reverse-k-group.png and b/notes/pics/reverse-k-group.png differ
diff --git a/tools/diagram/src/reverse-k-group.svg b/tools/diagram/src/reverse-k-group.svg
index 04a412c7..09f1d1f6 100644
--- a/tools/diagram/src/reverse-k-group.svg
+++ b/tools/diagram/src/reverse-k-group.svg
@@ -15,7 +15,7 @@
     .dash { stroke-dasharray: 5 4; }
     .line { stroke: #666; stroke-width: 1.3; fill: none; }
     .frame { fill: none; stroke: #999; stroke-width: 1; stroke-dasharray: 4 3; }
-    .shadow { fill: #C0C0C0; }
+    .shadow { fill: #DADADA; }
   </style>
   <defs>
     <marker id="a" viewBox="0 0 10 10" refX="9" refY="5" markerWidth="7" markerHeight="7" orient="auto-start-reverse">
@@ -32,27 +32,27 @@
 
   <text x="300" y="28" class="title">K 个一组翻转链表（k = 2）</text>
   <text x="20" y="90" class="b">翻转前</text>
-  <rect x="88" y="72" width="50" height="32" rx="6" class="shadow"/>
+  <rect x="87" y="71" width="50" height="32" rx="6" class="shadow"/>
   <rect x="85" y="69" width="50" height="32" rx="6" fill="#E6E6E6"/>
   <text x="110" y="89.5" class="c b">dummy</text>
   <line x1="137" y1="85" x2="163" y2="85" class="arrow "/>
-  <rect x="168" y="72" width="50" height="32" rx="6" class="shadow"/>
+  <rect x="167" y="71" width="50" height="32" rx="6" class="shadow"/>
   <rect x="165" y="69" width="50" height="32" rx="6" fill="#B1DDF0"/>
   <text x="190" y="89.5" class="c b">1</text>
   <line x1="217" y1="85" x2="243" y2="85" class="arrow "/>
-  <rect x="248" y="72" width="50" height="32" rx="6" class="shadow"/>
+  <rect x="247" y="71" width="50" height="32" rx="6" class="shadow"/>
   <rect x="245" y="69" width="50" height="32" rx="6" fill="#B1DDF0"/>
   <text x="270" y="89.5" class="c b">2</text>
   <line x1="297" y1="85" x2="323" y2="85" class="arrow "/>
-  <rect x="328" y="72" width="50" height="32" rx="6" class="shadow"/>
+  <rect x="327" y="71" width="50" height="32" rx="6" class="shadow"/>
   <rect x="325" y="69" width="50" height="32" rx="6" fill="#B1DDF0"/>
   <text x="350" y="89.5" class="c b">3</text>
   <line x1="377" y1="85" x2="403" y2="85" class="arrow "/>
-  <rect x="408" y="72" width="50" height="32" rx="6" class="shadow"/>
+  <rect x="407" y="71" width="50" height="32" rx="6" class="shadow"/>
   <rect x="405" y="69" width="50" height="32" rx="6" fill="#B1DDF0"/>
   <text x="430" y="89.5" class="c b">4</text>
   <line x1="457" y1="85" x2="483" y2="85" class="arrow "/>
-  <rect x="488" y="72" width="50" height="32" rx="6" class="shadow"/>
+  <rect x="487" y="71" width="50" height="32" rx="6" class="shadow"/>
   <rect x="485" y="69" width="50" height="32" rx="6" fill="#B1DDF0"/>
   <text x="510" y="89.5" class="c b">5</text>
   <line x1="110" y1="131" x2="110" y2="105" class="arrow "/>
@@ -64,27 +64,27 @@
   <line x1="350" y1="131" x2="350" y2="105" class="arrow "/>
   <text x="350" y="147" class="c ">next</text>
   <text x="20" y="205" class="b">翻转后</text>
-  <rect x="88" y="187" width="50" height="32" rx="6" class="shadow"/>
+  <rect x="87" y="186" width="50" height="32" rx="6" class="shadow"/>
   <rect x="85" y="184" width="50" height="32" rx="6" fill="#E6E6E6"/>
   <text x="110" y="204.5" class="c b">dummy</text>
   <line x1="137" y1="200" x2="163" y2="200" class="arrow "/>
-  <rect x="168" y="187" width="50" height="32" rx="6" class="shadow"/>
+  <rect x="167" y="186" width="50" height="32" rx="6" class="shadow"/>
   <rect x="165" y="184" width="50" height="32" rx="6" fill="#B1DDF0"/>
   <text x="190" y="204.5" class="c b">2</text>
   <line x1="217" y1="200" x2="243" y2="200" class="arrow "/>
-  <rect x="248" y="187" width="50" height="32" rx="6" class="shadow"/>
+  <rect x="247" y="186" width="50" height="32" rx="6" class="shadow"/>
   <rect x="245" y="184" width="50" height="32" rx="6" fill="#B1DDF0"/>
   <text x="270" y="204.5" class="c b">1</text>
   <line x1="297" y1="200" x2="323" y2="200" class="arrow "/>
-  <rect x="328" y="187" width="50" height="32" rx="6" class="shadow"/>
+  <rect x="327" y="186" width="50" height="32" rx="6" class="shadow"/>
   <rect x="325" y="184" width="50" height="32" rx="6" fill="#B1DDF0"/>
   <text x="350" y="204.5" class="c b">3</text>
   <line x1="377" y1="200" x2="403" y2="200" class="arrow "/>
-  <rect x="408" y="187" width="50" height="32" rx="6" class="shadow"/>
+  <rect x="407" y="186" width="50" height="32" rx="6" class="shadow"/>
   <rect x="405" y="184" width="50" height="32" rx="6" fill="#B1DDF0"/>
   <text x="430" y="204.5" class="c b">4</text>
   <line x1="457" y1="200" x2="483" y2="200" class="arrow "/>
-  <rect x="488" y="187" width="50" height="32" rx="6" class="shadow"/>
+  <rect x="487" y="186" width="50" height="32" rx="6" class="shadow"/>
   <rect x="485" y="184" width="50" height="32" rx="6" fill="#B1DDF0"/>
   <text x="510" y="204.5" class="c b">5</text>
   <line x1="110" y1="246" x2="110" y2="220" class="arrow "/>