diff --git a/TrappingRainWater.py b/TrappingRainWater.py
new file mode 100644
index 0000000..37af4af
--- /dev/null
+++ b/TrappingRainWater.py
@@ -0,0 +1,24 @@
+class Solution:
+  def trap(self, h: List[int]) -> int:
+    res = passed = maxV = last = 0
+    for i, v in enumerate(h):
+      if v > maxV:
+        res += passed
+        passed = 0
+        last = i
+        maxV = v
+      else:
+        passed += maxV - v
+        
+    passed = maxV = 0
+    for i, v in enumerate(h[::-1]):
+      if i >= len(h) - last:
+        break
+      elif v >= maxV:
+        res += passed
+        passed = 0
+        maxV = v
+      else:
+        passed += maxV - v
+    
+    return res